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CBSE Class 12 Physics - MCQ and Online Tests - Unit 8 - Electromagnetic Waves

CBSE Class 12 Physics – MCQ and Online Tests – Unit 8 – Electromagnetic Waves

Every year CBSE conducts board exams for 12th standard. These exams are very competitive to all the students. So our website provides online tests for all the 12th subjects. These tests are also very effective and useful for those who preparing for competitive exams like NEET, JEE, CA etc. It can boost their preparation level and confidence level by attempting these chapter wise online tests.

These online tests are based on latest CBSE Class 12 syllabus. While attempting these our students can identify the weak lessons and continuously practice those lessons for attaining high marks. It also helps to revise the NCERT textbooks thoroughly.

CBSE Class 12 Physics – MCQ and Online Tests – Unit 8 – Electromagnetic Waves

Question 1.
Maxwell’s equation involving \(\frac{d}{dt}\) \(\vec{B}\) is obtained-from:
(a) Ampere’s law
(b) Gauss’s law
(c) Faraday’s law
(d) Biot-Savart’s law

Answer

Answer: (c) Faraday’s law

Question 2.
Which of the following laws was modified by Maxwell by introducing the displacement current?
(a) Gauss’s law
(b) Ampere’s law
(c) Biot-Savart’s law
(d).None of these

Answer

Answer: (b) Ampere’s law

Question 3.
The dimensional formula of \(\vec{E}\) is:
(a)[MLT^-2A^-1]
(b) [MLT^-3A^-1]
(c) [MLT^-2A^-2]
(d) None of these

Answer

Answer: (b) [MLT^-3A^-1]

Question 4.
Electromagnetic waves have a speed of
(a) 3 × 10⁵ kms^-1
(b)3 × 10⁶ kms^-1
(c) 3 × 10⁷ kms^-1
(d) 3 × 10⁸ kms^-1

Answer

Answer: (a) 3 × 10⁵ kms^-1

Question 5.
The dimensions of \(\vec{E}\), \(\vec{dl}\) are identical to that of:
(a) potential
(b) charge
(c) current
(d) None of these

Answer

Answer: (a) potential

Question 6.
Which of the following EMW has highest wavelength?
(a) X-ray
(b) ultraviolet rays
(c) infrared rays
(d) microwaves

Answer

Answer: (c) infrared rays

Question 7.
The dimensional formula of is:
(a) [MLT^-2A^-1]
(b) [ML⁰T^-2A^-1]
(c) [ML⁰T^-3A^-1]
(d) None of these

Answer

Answer: (b) [ML⁰T^-2A^-1]

Question 8.
Displacement current is always :
(a) equal to conduction current
(b) less than conduction current
(c) greater than conduction current
(d) the sum of current due to flow of positive and negative ions

Answer

Answer: (a) equal to conduction current

Question 9.
Choose the wave relevant to telecommunication :
(a) ultraviolet
(b) infrared
(c) microwave
(d) visible light

Answer

Answer: (c) microwave

Question 10.
EMW are produced by:
(a) charge in uniform motion only
(b) charge at rest only
(c) accelerated or decelerated charge only
(d) all of the above

Answer

Answer: (c) accelerated or decelerated charge only

Question 11.
If \(\vec{B}\) is the magnetic field vector and \(\vec{E}\) is the electric field vector in an em wave, then which of the following relations is correct? Here c is the speed of fight:
(a) c = \(\frac{E}{B}\)
(b) c = BE
(c) c = \(\frac{B}{E}\)
(d) c = \(\frac{1}{EB}\)

Answer

Answer: (a) c = \(\frac{E}{B}\)

Question 12.
The dimensions of E/Bare same as that of:
(a) charge
(b) current
(c) velocity
(d) acceleration

Answer

Answer: (c) velocity

Question 13.
Name the law which states that a varying electric field produces a magnetic field:
(a) Biot-Savart’s law
(b) Faraday’s law
(c) Modified Ampere’s law
(d) None of these

Answer

Answer: (c) Modified Ampere’s law

Question 14.
The existence of EMW was experimentally established by :
(a) Sir S. C. Bose
(b) Maxwell
(c) Marconi
(d) Hertz

Answer

Answer: (a) Sir S. C. Bose

Question 15.
Displacement current is due to:
(a) the flow of electrons
(b) the Varying electric field
(c) the ionization of atmosphere
(d) the flow of protons

Answer

Answer: (b) the Varying electric field

Question 16.
Who first demonstrated the existence of em waves?
(a) Hertz
(b) Maxwell
(c) Ampere
(d) Faraday

Answer

Answer: (a) Hertz

Question 17.
Light Year is the unit of:
(a) distance
(b) time
(c) energy
(d) intensity of light

Answer

Answer: (a) distance

Question 18.
An EMW of v = 3 MHz passes from vacuum into dielectric medium with permittivity E_r = 4, then:
(a) Wavelength is doubled and the frequency remains unchanged
(b) Wavelength is doubled and the frequency become half
(c) Wavelength is halved and the frequency remains unchanged
(d) Wavelength and frequency both remain unchanged

Answer

Answer: (c) Wavelength is halved and the frequency remains unchanged

Question 19.
Frequency of a wave is 6 × 10¹⁵. Hz. The wave is :
(a) Radiowave
(b) Microwave
(c) X-ray
(d) Ultra violet

Answer

Answer: (d) Ultra violet

Question 20.
If u_e and u_m arc the electric and magnetic field densities in an electromagnetic wave, then (c is the speed of light):
(a) u_e = u_m
(b) u_e = c u_m
(c) u_e = \(\frac{u_m}{c}\)
(d) None of these

Answer

Answer: (a) u_e = u_m

Question 21.
Solar radiation is :
(a) transverse EMW
(b) longitudinal EMW
(c) both (a) and (b)
(d) None of these

Answer

Answer: (a) transverse EMW

Question 22.
Choose the wrong statement?
(a) Electromagnetic waves are transverse
(b) Electromagnetic waves travel with the speed of light in free space
(c) Electromagnetic waves are produced by accelerating charges
(d) Electromagnetic waves travel with the same speed in all media

Answer

Answer: (d) Electromagnetic waves travel with the same speed in all media

Question 23.
Which of the following has the dimensions of current?
(a) ε₀ \(\vec{E}\).\(\vec{dt}\)
(b) µ₀ \(\vec{E}\).\(\vec{dt}\)
(c) \(\frac{\vec{B}.\vec{dl}}{µ_0}\)
(d) \(\frac{\vec{B}.\vec{dl}}{ε_0}\)

Answer

Answer: (c) \(\frac{\vec{B}.\vec{dl}}{µ_0}\)

Question 24.
Which of the following has the dimensions of charge?
(a) \(\frac{ε_0\vec{E}}{\vec{ds}}\)
(b) µ₀ \(\vec{E}\).\(\vec{ds}\)
(c) \(\frac{ε_0}{µ_0}\) \(\vec{E}\).\(\vec{ds}\)
(d) \(\frac{µ_0}{ε_0}\) \(\vec{E}\).\(\vec{ds}\)

Answer

Answer: (a) \(\frac{ε_0\vec{E}}{\vec{ds}}\)

Question 25.
Ampere’s circuital law was modified by:
(a) Laplace
(b) Gauss
(c) Maxwell
(d) Hertz

Answer

Answer: (c) Maxwell

CBSE Class 12 Physics - MCQ and Online Tests - Unit 7- Alternating Current

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CBSE Class 12 Physics – MCQ and Online Tests – Unit 7- Alternating Current

Question 1.
In series resonant circuit:
(a) reactance is zero
(b) current is zero
(c) voltage is zero
(d) None of these

Answer

Answer: (d) None of these

Question 2.
The dimensional formula of impedance is;
(a) [ML²T^-2A^-2]
(b) [ML²T^-3A^-2]
(c) [ML²T^-2A^-1]
(d) [ML²T^-2A^-3]

Answer

Answer: (b) [ML²T^-3A^-2]

Question 3.
Energy dissipates in LCR circuit in :
(a) L only
(b) C only
(c) R only
(d) All of the above

Answer

Answer: (c) R only

Question 4.
Which of the following has dimensions different from the rest?
(a) L/R
(b) \(\frac{1}{RC}\)
(c) \(\sqrt{LC}\)
(d) RC

Answer

Answer: (b) \(\frac{1}{RC}\)

Question 5.
What is the ratio of inductive and capacitance reactances in an ac circuit?
(a) 1
(b) ω²L
(c) ω²LC
(d) l

Answer

Answer: (c) ω²LC

Question 6.
The no. of turns in the primary coil of a transformer is 200 and the no. of turns in the secondary is 10. If 240 V a.c. is applied to primary, the output from the secondary
(a) 6 V
(b) 12 V
(c) 24 V
(d) 48 V

Answer

Answer: (b) 12 V

Question 7.
An acceptor circuit is :
(a) series resonant circuit
(b) parallel resonant circuit
(c) LCR circuit
(d) None of these

Answer

Answer: (a) series resonant circuit

Question 8.
In parallel resonant circuit:
(a) impedance is very high
(b) current is very high
(c) voltage is very high
(d) None of these

Answer

Answer: (a) impedance is very high

Question 9.
The dimensional formula of L/R is similar to that of:
(a) frequency
(b) time
(c) length
(d) none of these

Answer

Answer: (b) time

Question 10.
Transformer works on the principle of:
(a) convertor
(b) invertor
(c) mutual induction
(d) self-induction

Answer

Answer: (c) mutual induction

Question 11.
An ac ammeter connected in series in an ac circuit reads 5A. The peak value of current:
(a) 5 A
(b) 5√2A
(c) \(\frac{5}{√5}\) A
(d) zero

Answer

Answer: (b) 5√2A

Question 12.
The phase difference b/w the A.C. and e.m.f. \(\frac{π}{2}\) Which of the following can not be the instituent of the circuit?
(a) LC
(b) L alone
(c) C alone
(d) RL

Answer

Answer: (d) RL

Question 13.
The band width of a series resonant circuit is :
(a) f₀/Q₀
(b) \(\frac{R}{2πL}\)
(c) \(\frac{R}{4πL}\)
(d) 4R

Answer

Answer: (a) f₀/Q₀

Question 14.
An iron core transformer with a turns ratio of 8 : 1 has 120 V applied across the primary. The voltage across the
(a) 15 V
(b) 120 V
(c) 180 V
(d) 960 V

Answer

Answer: (a) 15 V

Question 15.
The Q factor of an LCR circuit at resonance is :
(a) \(\sqrt{R^2+ω^2L^2}\)
(b) \(\sqrt{R^2+(\frac{1}{cω}})^2\)
(c) \(\frac{ω_rL}{R}\)
(d) \(\sqrt{R^2+\frac{1}{c^2ω^2}}\)

Answer

Answer: (c) \(\frac{ω_rL}{R}\)

Question 16.
A broadcast circute broadcasts at 300 m band. A condenser of capacitance 2.4 lµF is available. The value of the inductance required for resonant circuit is:
(a) 10^-4 H
(b) 10^-8 H
(c) 10^-6 H
(d) 10^-2 H

Answer

Answer: (b) 10^-8 H

Question 17.
Faraday constant:
(a) depends on the amount of the electrolyte
(b) depends on the current in the electrolyte
(c) is a universal constant
(d) depends on the amount of charge passed through the electrolyte

Answer

Answer: (c) is a universal constant

Question 18.
In the series L-C-R circuit, the voltmeter and ammeter readings are:
MCQ Questions for Class 12 Physics Chapter 7 Alternating Current with Answers
(a) V = 100 Volts, I = 2A
(b) V = 100 Volts, I = 5A
(c) V = 1000 Volts, I = 2A
(d) V = 300 Volts, I = 1A

Answer

Answer: (a) V = 100 Volts, I = 2A

Question 19.
The average power dissipation in pure inductance or capacitance is:
(a) \(\frac{1}{2}\) LI²
(b) \(\frac{3}{2}\) CV²
(c) either (a) or (b)
(d) zero

Answer

Answer: (d) zero

Question 20.
Two coils X and Y are connected in series across a 240 V, 50 Hz supply. The resistance of X is 5Ω and inductance of Y is 0.02 H. The power consumed is 3 kW and the power factor is 0.75. The impedance of the circuit is:
(a) 0.144 Ω
(b) 1.44 Ω
(c) 14.4 Ω
(d) 144 Ω

Answer

Answer: (c) 14.4 Ω

Question 21.
A rejector circuit is:
(a) series resonant circuit
(b) parallel resonant circuit
(c) LCR circuit
(d) None of these

Answer

Answer: (b) parallel resonant circuit

Question 22.
Which of the following effects is not shown in alternating current ?
(a) Chemical effect
(b) Magnetic effect
(c) Heating current
(d) All of these

Answer

Answer: (a) Chemical effect

Question 23.
The inductive reactance of an inductor coil of \(\frac{1}{π}\) H at 50 Hz is:
(a) \(\frac{50}{π}\) Ω
(b) \(\frac{π}{50}\) Ω
(c) 100 Ω
(d) 50 Ω

Answer

Answer: (c) 100 Ω

Question 24.
The average value of a cover a complete cycle is:
(a) l₀
(b) \(\frac{l_0}{2}\)
(c) \(\frac{l_0}{√2}\)
(d) zero

Answer

Answer: (d) zero

Question 25.
The natural frequency of an L -C-Circuit is equal to :
(a) \(\frac{\sqrt{LC}}{2π}\)
(b) \(\frac{1}{3π\sqrt{LC}}\)
(c) \(\frac{1}{2π}\sqrt{\frac{L}{C}}\)
(d) \(\frac{1}{2π}\sqrt{\frac{C}{L}}\)

Answer

Answer: (b) \(\frac{1}{3π\sqrt{LC}}\)

Question 26.
An electric circuit containing capacitor only suffers:
(a) equal resistance for A.C. and D.C.
(b) Resistance of A.C. > Resistance of D.C.
(c) Resistance for A.C. < Resistance of D.C.
(d) offers infinite resistance for D.C.

Answer

Answer: (d) offers infinite resistance for D.C.

Question 27.
Power factor of an ac circuit is a measure of:
(a) virtual power
(b) power lost in the circuit
(c) mean power
(d) all the above

Answer

Answer: (b) power lost in the circuit

Question 28.
The current through an inductor of 1H is given by I = 3t sin t. The voltage across the inductor of 1 H is:
(a) 3 sin t + 3 cos t
(b) 3 sin t + 3t cos t
(c) 3 cos t + t sin t
(d) 3t cos t + sin t

Answer

Answer: (b) 3 sin t + 3t cos t

Question 29.
In the above problem, the value of the resistance of the coil Y is:
(a) 0.58 Ω
(b) 5.8 Ω
(c) 1.16 Ω
(d) 11.6 Ω

Answer

Answer: (b) 5.8 Ω

Question 30.
In pure inductive circuit current
(a) lags behind emf by π/2
(b) leads the emf by π/2
(c) lags behind emf by π
(d) leads the emf by π

Answer

Answer: (a) lags behind emf by π/2

CBSE Class 12 Physics - MCQ and Online Tests - Unit 6 - Electromagnetic Induction

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CBSE Class 12 Physics – MCQ and Online Tests – Unit 6 – Electromagnetic Induction

Question 1.
In a uniform magnetic field B, a wire in the form of a semicircle of radius r rotated about the diameter of the circle with angular frequency ‘ω’. The axis of rotation is perpendicular to the field. If the total resistance of the circuit is R the mean power generated per period of rotation is :
(a) \(\frac{Bπr^2ω}{2R}\)
(b) \(\frac{(Bπr^2ω)^2}{8R}\)
(c) \(\frac{(Bπrω)^2}{2R}\)
(d) \(\frac{(Bπrω^2)^2}{8R}\)

Answer

Answer: (b) \(\frac{(Bπr^2ω)^2}{8R}\)

Question 2.
An e^– and a p^– are moving parallel to each other in a magnetic field. The magnetic force acting on the p⁺ is:
(a) 1840 times that on e^–
(b) less than that of e^–
(c) same as that of e^–
(d) slightly more than that of e^–

Answer

Answer: (c) same as that of e^–

Question 3.
A transformer is used to light 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 A. Then the efficiency of the transformer is:
(a) 11%
(b) 50%
(c) 80%
(d) 90%

Answer

Answer: (d) 90%

Question 4.
The magnetic flux (∅) lined with a coil is related to its area (s) as:
(a) ∅ ∝ s
(b) ∅ ∝ s²
(c) ∅ ∝ s^1/2
(d) ∅ ∝ s^-1/2

Answer

Answer: (a) ∅ ∝ s

Question 5.
The coupling co-efficient of the perfectly coupled coils is:
(a) Zero
(b) 1
(c) slightly more than 1
(d) infinite

Answer

Answer: (b) 1

Question 6.
If the magnetic flux linked with a coil through which a current off ampere is set up is ∅, then the coefficient of self-inductance of the coil is:
(a) \(\frac{l}{∅}\)
(b) \(\frac{∅}{l}\)
(c) ∅l
(d) None of these

Answer

Answer: (b) \(\frac{∅}{l}\)

Question 7.
The magnetic field is parallel to a surface, then the magnetic flux through the surface is :
(a) zero
(b) small but not zero
(c) infinite
(d) large but not infinite

Answer

Answer: (b) small but not zero

Question 8.
The role of inductance is equivalent to:
(a) inertia
(b) force
(c) energy
(d) momentum

Answer

Answer: (a) inertia

Question 9.
The flux linked with a coif at any instant t is given by ∅ = 10t² – 50t + 250. The induced emf at t = 35 is:
(a) 10 V
(b) 190 V
(c) -190 V
(d) -10 V

Answer

Answer: (d) -10 V

Question 10.
In the expression e = –\(\frac{d∅}{dt}\), the -ve sign signifies:
(a) The induced emf is produced only when magnetic flux decreases
(b) The induced emf opposes the change in the magnetic flux
(c) The induced emf is opposite to the direction of the flux
(d) None of these

Answer

Answer: (b) The induced emf opposes the change in the magnetic flux

Question 11.
A metal conductor of length 1 m rotates vertically about one of its ends at angular velocity 5 rad s^-1 . If the horizontal component of earth’s magnetism is 2 × 10^-5 T, then e.m.f. developed between the two ends of the conductor is:
(a) 5 µV
(b) 50 µV
(c) 5 mV
(d) 50 mV

Answer

Answer: (a) 5 µV

Question 12.
1 henry is equal to :
(a) \(\frac{weber}{ampere}\)
(b) \(\frac{weber}{Volt}\)
(c) weber ampere
(d) None of these

Answer

Answer: (a) \(\frac{weber}{ampere}\)

Question 13.
The magnetic flux (∅) linked with a coil is related to the number of turns (N) ofthe coil as:
(a) f ∝ N
(b) f ∝ N^-1
(c) f ∝ N²
(d) f ∝ N^-2

Answer

Answer: (a) f ∝ N

Question 14.
coil of L = 8.4 mH and R = 6 Ω is connected to a 12 V battery. The current in the coil is 1.0 A at approx’time of:
(a) 500 s
(b) 20 s
(c) 35 ms
(d) 1 ms

Answer

Answer: (d) 1 ms

Question 15.
The core of a transformer is laminated because:
(a) rusting of core may be prevented
(b) ratio of voltage in primary and secondary may be increased.
(c) energy losses due to eddy current may be minimised
(d) The weight of transformer may be reduced

Answer

Answer: (c) energy losses due to eddy current may be minimised

Question 16.
If I current is flowing inductance L, then the dimension of \(\frac{3}{2}\) LI² is equivalent to:
(a) charge
(b) force
(c) momentum
(d) energy

Answer

Answer: (c) momentum

Question 17.
A choke is used as a resistance in :
(a) dc circuits
(b) ac circuits
(c) both ac and dc circuits
(d) neither (a) nor (b)

Answer

Answer: (b) ac circuits

Question 18.
For purely capacitive circuits, power factor is:
(a) 0
(b) -1
(c) 1
(d) infinity

Answer

Answer: (a) 0

Question 19.
The magnetic flux linked with a coil is inversely proportional to the?
(a) magnetic field
(b) area of cross section
(c) number of turns
(d) none of these

Answer

Answer: (a) magnetic field

Question 20.
Which of the following is not equal to a henry?
(a) \(\frac{Volt second}{ampere}\)
(b) \(\frac{Volt second^2}{Coulomb}\)
(c) \(\frac{Volt^2 second}{Coulomb}\)
(d) \(\frac{Jole second}{Coulomb^2}\)

Answer

Answer: (c) \(\frac{Volt^2 second}{Coulomb}\)

Question 21.
When the magnetic field is parallel to a surface, then the magnetic flux through the surface is:
(a) infinite
(b) zero
(c) small but not zero
(d) large but not infinite.

Answer

Answer: (b) zero

Question 22.
The phase difference between the flux linkage and the emf in a rotating coil in a uniform magnetic field is:
(a) zero
(b) \(\frac{π}{2}\)
(c) \(\frac{π}{4}\)
(d) π

Answer

Answer: (c) \(\frac{π}{4}\)

Question 23.
The energy stored in a 50 mH inductor carrying a current of 4 A is:
(a) 0.1 J
(b) 0.4 J
(c) 0.04 J
(d) 0.01 J

Answer

Answer: (b) 0.4 J

Question 24.
Two coils of self inductance 2 mil and 8 mil are placed so close together that the effective flux in one coil is completely linked with other. The mutual inductance between these coils is :
(a) 4 mH
(b) 16 mH
(c) 10 mH
(d) 6 mH

Answer

Answer: (c) 10 mH

Question 25.
The SI unit of magnetic flux is:
(a) T
(b) Tn^-2
(c) Wb
(d) Wb m^-2

Answer

Answer: (c) Wb

CBSE Class 12 Physics - MCQ and Online Tests - Unit 5 - Magnetism and Matter

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CBSE Class 12 Physics – MCQ and Online Tests – Unit 5 – Magnetism and Matter

Question 1.
A magnetic bar of M magnetic moment is placed m the field of magnetic strength B, the torque acting on it is :
(a) \(\vec{M} \).\(\vec{B} \)
(b) –\(\vec{M} \).\(\vec{B} \)
(c) \(\vec{M} \) × \(\vec{B} \).
(d) \(\vec{B} \) × \(\vec{M} \)

Answer

Answer: (c) \(\vec{M} \) × \(\vec{B} \).

Question 2.
What is the magnetic field in the empty space enclosed by the toroidal solenoid of radius ‘R’? ,
(a) Infinity
(b) \(\frac{µ_0}{4π}\).\(\frac{2πl}{R}\)
(c) \(\frac{µ_0}{4π}\).(\(\frac{πl}{R}\))
(d) zero

Answer

Answer: (d) zero

Question 3.
On quadrupling the moment of inertia of a magnet, its frequency of oscillation will become:
(a) half
(b) double
(c) four times
(d) one-fourth

Answer

Answer: (a) half

Question 4.
The dimensional representation of magnetic flux density is :
(a) [MLT^-2]
(b) [MLT^-2A^-1]
(c) [MLT^-2A^-2]
(d) [MT^-2A^-1]

Answer

Answer: (d) [MT^-2A^-1]

Question 5.
S.I. unit of flux is :
(a) Ohm
(b) Weber
(c) Tesla
(d) None

Answer

Answer: (b) Weber

Question 6.
What is the angle of dip at a place where the horizontal component of earth’s magnetic field is equal to the vertical component?
(a) 0°
(b) 30°
(c) 45°
(d) 90°

Answer

Answer: (c) 45°

Question 7.
In a moving coil galvanometer, we use a radial magnetic field so that the galvanometer scale is :
(a) exponential
(b) linear
(c) algebraic
(d) logarithmic

Answer

Answer: (b) linear

Question 8.
Tangent law is applicable only when:
(a) two uniform and mutually perpendicular magnetic fields exist
(b) two magnetic fields exist
(c) horizontal component of earth’s magnetic field is present
(d) uniform magnetic field are used

Answer

Answer: (a) two uniform and mutually perpendicular magnetic fields exist

Question 9.
A current carrying power line carries current from west to east. What will be direction of magnetic field 1 meter above it?
(a) N to S
(b) S to N
(c) E to W
(d) W to E

Answer

Answer: (a) N to S

Question 10.
A magnetic dipole moment is a vector quantity directed from:
(a) S to N
(b) N to S
(c) E to W
(d) W to E

Answer

Answer: (a) S to N

Question 11.
The neutral point in the magnetic field of a horizontally placed bar magnet is a point where the magnetic field due to that bar magnet is:
(a) zero
(b) more than that of earth
(c) less than that of earth
(d) equal to that of earth

Answer

Answer: (d) equal to that of earth

Question 12.
The force acting per unit length of a semi circular wire of radius R carrying a current I is:
(a) \(\frac{µ_0l^2}{4R}\)
(b) \(\frac{µ_0l^2}{2R}\)
(c) \(\frac{µ_0l^2}{R}\)
(d) \(\frac{2µ_0l^2}{R}\)

Answer

Answer: (a) \(\frac{µ_0l^2}{4R}\)

Question 13.
The dimensional representation of \(\sqrt{l/MB}\) is similar to that of:
(a) frequency
(b) time
(c) distance
(d) speed

Answer

Answer: (b) time

Question 14.
The radius of curvature of the path of charged particle in a uniform magnetic file is directly proportional to the
(a) charge on fie particle
(b) Momentum of particle
(c) energy of particle
(d) Strength of field

Answer

Answer: (b) Momentum of particle

Question 15.
Which of the following has a low value in ferrites?
(a) Conductivity
(b) Permeability
(c) Magnetic susceptibility
(d) All the above

Answer

Answer: (a) Conductivity

Question 16.
Which of the following has higher magnetic susceptibility?
(a) diamagnetic
(b) paramagnetic
(c) ferromagnetic
(d) None of these

Answer

Answer: (c) ferromagnetic

Question 17.
The force between two parallel wire 2 × 10^-7 Nm^-1, placed 1 m apart to each other in vacuum. The electric current flowing through the wires is:
(a) 1 A
(b) zero
(c) 5 × 10⁶ A
(d) 2 × 10^-7 A

Answer

Answer: (a) 1 A

Question 18.
In a bar magnet, magnetic lines of force z :
(a) are produced only at north pole like rays of light from a bulb
(b) starts from north pole and ends at the south pole
(c) emerge in circular paths from the middle of the bar
(d) run continuously through the bar and outside

Answer

Answer: (b) starts from north pole and ends at the south pole

Question 19.
The Mariner’s compass is provided with Gimbals arrangement so as to :
(a) keep the needle always horizontal
(b) give a direct reading of declination
(c) give the direct value of dip
(d) all of the above

Answer

Answer: (c) give the direct value of dip

Question 20.
Ferrites may be:
(a) ant. ferromagnetic
(b) ferromagnetic
(c) ferrimagnetic
(d) None of the above

Answer

Answer: (b) ferromagnetic

Question 21.
A wire of length I has a magnetic moment M. It is then bent into a semi-circular arc. The neyv magnetic moment is :
(a) M
(b) M.l.
(c) \(\frac{2M}{π}\)
(d) \(\frac{M}{π}\)

Answer

Answer: (c) \(\frac{2M}{π}\)

Question 22.
The magnetic field strength due to a short bar magnet directed along its axial line at a distance r is B. What is its value at the same distance along the equatorial line?
(a) B
(b) 2B
(c) \(\frac{B}{2}\)
(d) \(\frac{B}{4}\)

Answer

Answer: (c) \(\frac{B}{2}\)

Question 23.
The magnetic lines of force inside a bar magnet:
(a) do not exist
(b) depends on area of cross-section of bar magnet
(c) are from N-pole to S-pole of the magnet
(d) are from S-pole to N-pole of the magnet.

Answer

Answer: (d) are from S-pole to N-pole of the magnet.

Question 24.
The relation between geometric length (L) and magnetic length (L_m) is:
(a) L_m = \(\frac{5}{6}\) L_g
(b) L_m = \(\frac{6}{5}\) L_g
(c) (a) L_m = L_g
(d) L_m = 2RY;UL L_g

Answer

Answer: (a) L_m = \(\frac{5}{6}\) L_g

Question 25.
The magnetic field of earth is due to:
(a) induction effect of the sun
(b) the presence of a large magnet at the centre of the earth
(c) interaction of cosmic rays with the current of earth
(d) motion and distribution of some material in an outside the earth

Answer

Answer: (d) motion and distribution of some material in an outside the earth

CBSE Class 12 Physics - MCQ and Online Tests - Unit 4 - Moving Charges and Magnetism

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CBSE Class 12 Physics – MCQ and Online Tests – Unit 4 – Moving Charges and Magnetism

Question 1.
A charged particle of mass m and charge q travels on a circular path of radius r i.e., perpendicular to the magnetic field B. The time taken by particle to complete on revolution is :
(a) \(\frac{2πqB}{m}\)
(b) \(\frac{2πm}{qB}\)
(c) \(\frac{2πmq}{B}\)
(d) \(\frac{2πq^2B}{m}\)

Answer

Answer: (b) \(\frac{2πm}{qB}\)

Question 2.
When we double the radius of a coil keeping the current through it unchanged, what happens to the magnetic field directed along its axis at far off points?
(a) halved
(b) doubled
(c) quadrupled
(d) remains unchanged

Answer

Answer: (d) remains unchanged

Question 3.
The sensitivity of a tangent galvanometer can be increased by increasing:
(a) the radius of the coil
(b) the external magnetic field
(c) the number of turns of the coil
(d) all the above

Answer

Answer: (b) the external magnetic field

Question 4.
A current carring coil is placed in a uniform magnetic field. If the coil turns through an angle θ, then the torque is directly proportional to:
(a) sin θ
(b) cos θ
(c) cot θ
(d) tan θ

Answer

Answer: (b) cos θ

Question 5.
Which of the following is not a unit of magnetic induction?
(a) gauss
(b) tesla
(c) oersted
(d) weber/metre²

Answer

Answer: (c) oersted

Question 6.
The strength of the magnetic field around an infinite current carrying conductor is :
(a) same everywhere
(b) inversely proportional to the distance
(c) directly proportional to the distance
(d) None of these

Answer

Answer: (b) inversely proportional to the distance

Question 7.
A current carrying power line carries current from west to east. Then the direction of the magnetic field 2 m above it is :
(a) west to east
(b) south to north
(c) north to south
(d) None of these

Answer

Answer: (c) north to south

Question 8.
According to Ampere’s Circuital law
MCQ Questions for Class 12 Physics Chapter 4 Moving Charges and Magnetism with Answers

Answer

Answer: (b)

Question 9.
The force between two parallel current carrying conductors is F. If the current in each conductor is doubled, then the force between them becomes :
(a) 4F
(b) 2F
(c) F
(d) \(\frac{F}{4}\)

Answer

Answer: (a) 4F

Question 10.
What happens to the magnetic field at the centre of a circular current carrying coil if we double the radius of the coil keeping the current unchanged?
(a) halved
(b) doubled
(c) quadrupled
(d) remains unchanged

Answer

Answer: (a) halved

Question 11.
How much force will be experienced by a moving charge in a magnetic field? The symbols have their usual meanings.
(a) \(\vec{F}\) = q(\(\vec{v}\).\(\vec{B}\))
(b) \(\vec{F}\) = \(\frac{q}{(\vec{v}.\vec{B})}\)
(c) \(\vec{F}\) = \(\frac{q}{2}\)\((\vec{v}×\vec{B}\))
(d) \(\vec{F}\) = q(\(\vec{v}\)×\(\vec{B}\))

Answer

Answer: (d) \(\vec{F}\) = q(\(\vec{v}\)×\(\vec{B}\))

Question 12.
The magnetic field produced by an / meter long straight (x cry thin) current (I) carry ing conductor at any point on itself is :
(a) zero
(b) infinite
(c) \(\frac{µ_0l}{4πl}\)
(d) \(\frac{µ_0l}{2πl}\)

Answer

Answer: (a) zero

Question 13.
The current sensitibility of a moving coil galanometer increases with decrease in:
(a) magnetic field
(b) area of a coil
(c) number of turns
(d) None of these

Answer

Answer: (d) None of these

Question 14.
A charge + q is sent through a magnetic field. The force acting on it is maximum w hen the angle between the direction of motion of the charged particle and the magnetic field :
(a) 0°
(b) 45°
(c) 90°
(d) 180°

Answer

Answer: (c) 90°

Question 15.
A charge q moves in a region, where electric field E and magnetic field B both exist, then force on it is :
(a) \(\vec{F}\) = q(\(\vec{v}\)×\(\vec{B}\))
(b) \(\vec{F}\) = q{\(\vec{E}\)×(\(\vec{v}\) × \(\vec{B}\))}
(c) \(\vec{F}\) = q(\(\vec{E}\) + (\(\vec{B}\) × \(\vec{v}\))
(d) \(\vec{F}\) = q(\(\vec{B}\) + (\(\vec{E}\) ×\(\vec{v}\))

Answer

Answer: (b) \(\vec{F}\) = q{\(\vec{E}\)×(\(\vec{v}\) × \(\vec{B}\))}

Question 16.
An electron having mass ‘m’ and Kinetic energy E enters in uniform magnetic field B perpendicular, then its frequency will be:
(a) \(\frac{eE}{qmB}\)
(b) \(\frac{2πm}{eB}\)
(c) \(\frac{eB}{2πm}\)
(d) \(\frac{2m}{eBE}\)

Answer

Answer: (c) \(\frac{eB}{2πm}\)

Question 17.
A wire of length 2 metre carries a current 1 ampere, is bent to form a circle. The magnetic moment of the coil is :
(a) 2π
(b) π/2
(c) π/4
(d) 1/π

Answer

Answer: (d) 1/π

Question 18.
The magnetic field of a given length of a ware for single turn coil at its centre is B. Then.its value for two turns of coil will be :
(a) B/4
(b) B/2
(c) 4B
(d) 2B

Answer

Answer: (c) 4B

Question 19.
According to Gauss’s theorem in magnetism, surface integral of magnetic field intensity over a surface (closed or open) is always:
(a) -1
(b) 1
(c) 0
(d) infinity

Answer

Answer: (c) 0

Question 20.
When charged particle enters-a uniform magnetic field, its K.E.:
(a) remains constant
(b) increases
(c) decreases
(d) becomes zero

Answer

Answer: (a) remains constant

Question 21.
To convert galvanometer into voltmeter one should connect :
(a) high resistance in series with galvanometer
(b) low resistance in series with galvanometer
(c) high resistance in parallel with galvanometer
(d) low resistance in parallel with galvanometer

Answer

Answer: (a) high resistance in series with galvanometer

Question 22.
Isoclinic lines are the lines joining places with :
(a) equal dip
(b) equal declination
(cj equal dip and declination
(d) None of these

Answer

Answer: (a) equal dip

Question 23.
Two identical bar magnets each of dipole moment p and length I are perpendicular to each other as shown in Fig. The dipole moment of the combination is:
MCQ Questions for Class 12 Physics Chapter 4 Moving Charges and Magnetism with Answers
(a) √2 p
(b) \(\frac{p}{√2}\)
(c) P
(d) 2p

Answer

Answer: (a) √2 p

Question 24.
The SI unit of magnetic dipole moment is’
(a) Ampere
(b) Ampere metre²
(c) Tesla
(d) None of these

Answer

Answer: (b) Ampere metre²

Question 25.
Earth’s magnetism was discovered by:
(a) Gauss
(b) Oersted
(c) Ampere
(d) Gilbert

Answer

Answer: (d) Gilbert

Question 26.
The force \(\vec{F}\) experienced by a particle of charge q moving with velocity \(\vec{v}\) in a magnetic field \(\vec{B}\) is given by,
(a) \(\vec{F}\) = q(\(\vec{F}\) × \(\vec{B}\))
(b) \(\vec{F}\) = q(\(\vec{B}\) × (\(\vec{b}\))
(c) \(\vec{F}\) = q(\(\vec{v}\) × (\(\vec{B}\))
(d) \(\vec{F}\) = q(\(\vec{v}\) × \(\vec{B}\))

Answer

Answer: (a) \(\vec{F}\) = q(\(\vec{F}\) × \(\vec{B}\))

Question 27.
Tesla is a unit of:
(a) electric flux
(b) magnetic flux
(c) magnetic field
(d) electric field

Answer

Answer: (c) magnetic field

Question 28.
The permeability of a paramagnetic substance is:
(a) very large
(b) small but more than unity
(c) less than unity
(d) negative

Answer

Answer: (b) small but more than unity

Question 29.
What is the angle of dip at the magnetic poles ?
(a) 30°
(b) 0°
(c) 45°
(d) None of these

Answer

Answer: (d) None of these

Question 30.
10 eV electron is circulating in a plane at right angle to a uniform field of magnetic induction 10^-1 Wb/m² (1G). The orbital radius of electron is:
(a) 12 cm
(b) 16 cm
(c) 11 cm
(d) 18 cm

Answer

Answer: (c) 11 cm

Question 31.
Which of the following shows that the earth behaves as a magnet?
(a) Repulsion between like poles .
(b) Attraction between unlike poles
(c) Null points in the magnetic field of a bar magnet
(d) No existence of isolated magnetic poles

Answer

Answer: (c) Null points in the magnetic field of a bar magnet

Question 32.
A cyclotron can be used to produce high energy:
(a) neutrons
(b) deutrons
(c) β particles
(d) α partifcles

Answer

Answer: (d) α partifcles

Question 33.
The radius of the trajectory of a charged particle in a uniform magnetic field is proportional to the:
(a) charge on the particle
(b) energy of the particle
(c) momentum of the particle
(d) all the above

Answer

Answer: (c) momentum of the particle

Question 34.
The most suitable metal for making permanent magnets is :
(a) iron
(b) steel
(c) copper
(d) aluminium

Answer

Answer: (b) steel

Question 35.
Circular loop of radius 0.0157 m carries a current 2 A. The magnetic field at the centre of the loop is :
(a) 1.57 × 10^-3Wb/m²
(b) 8.0 × 10^-5 Wb/m²
(c) 2.0 × 10^-3 Wb/m²
(d) 3.l4 × 10^-1 Wb/m²

Answer

Answer: (b) 8.0 × 10^-5 Wb/m²

CBSE Class 12 Physics - MCQ and Online Tests - Unit 3 - Current Electricity

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CBSE Class 12 Physics – MCQ and Online Tests – Unit 3 – Current Electricity

Question 1.
Two wires of copper are of the same length but’have different diameters. When they are connected in series across a battery, the heat generated is H₁ When connected in parallel across the same battery, the heat generated during the same time is H₂ Then :
(a) H₁ = H₂
(b) H₁ < H₂
(c) H₁ > H₂
(d) H₁ > H₂

Answer

Answer: (b) H₁ < H₂

Question 2.
The example of a non-ohmic resistance is:
(a) copper wire
(b) fi lament lamp
(c) carbon resistor
(d) diode

Answer

Answer: (d) diode

Question 3.
The specific resistance of a rod of copper as compared to that of thin wire of copper is :
(a) less
(b) more
(c) same
(d) depends upon the length and area of cross-section of the wire

Answer

Answer: (c) same

Question 4.
A wire of resistance 3 Ω is cut into three pieces, which are then joined to form a triangle. The equivalent resistance between any corners of the triangle is :
(a) \(\frac{2}{3}\) Ω
(b) \(\frac{3}{2}\) Ω
(c) \(\frac{1}{2}\) Ω
(d) \(\frac{1}{3}\) Ω

Answer

Answer: (a) \(\frac{2}{3}\) Ω

Question 5.
The length of a conductor is halved. Its resistance will be :
(a) halved
(b) doubled
(c) unchanged
(d) quadrupled

Answer

Answer: (a) halved

Question 6.
If a certain piece of copper is to be shaped into a conductor of minimum resistance, its length (L) and cross-sectional area (a) shall respectively be :
(a) L, 2A
(b) \(\frac{L}{2}\), 2A
(c) 2L, 2A
(d) 2l, \(\frac{A}{2}\)

Answer

Answer: (b) \(\frac{L}{2}\), 2A

Question 7.
Given three equal resistors, how many different combinations (taken all of them together) can be made?
(a) 3
(b) 4
(c) 5
(d) 6

Answer

Answer: (b) 4

Question 8.
Siemen is the unit of:
(a) resistance
(b) conductance
(c) specific conductance
(d) None of these

Answer

Answer: (b) conductance

Question 9.
The speed at which tjie current travels in a conductor is nearly:
(a) 3 × 10⁴ ms^-1
(b) 3 × 10⁶ ms^-1
(c) 3 × 10⁸ ms^-1
(d) 3 × 10¹⁰ ms^-1

Answer

Answer: (a) 3 × 10⁴ ms^-1

Question 10.
In the above question, the conductance:
(a) halved
(b) doubled
(c) unchanged
(d) quadrupled

Answer

Answer: (b) doubled

Question 11.
Specific resistance of ali metals is mostly affected by:
(a) temperature
(b) pressure
(c) magnetic field
(d) volume

Answer

Answer: (a) temperature

Question 12.
How much electric energy is consumed by a 100 W lamp used for 6 hours everyday for 30 days?
(a) 18 kJ
(b) 18 kWh
(c) 1.8 J
(d) None of these

Answer

Answer: (b) 18 kWh

Question 13.
How many different resistances are possible with two equal resistors?
(a) 2
(b) 3
(c) 4
(d) 5

Answer

Answer: (b) 3

Question 14.
The number of electrons that constitute 1 A of current is:
(a) 6.25 × 10¹⁶
(b) 6.25 × 10¹⁷
(c) 6.25 × 10¹⁸
(d) 6.25 × 10¹⁹

Answer

Answer: (c) 6.25 × 10¹⁸

Question 15.
Suppose H₁ is the heat generated per second in the filament of a 100 W, 250 V lamp and H₂ is the heat generated in the filament of a 200 W, 250 V lamp. Then H₁/H₂ is equal to:
(a) 1
(b) 2
(c) \(\frac{1}{2}\)
(d) \(\frac{1}{4}\)

Answer

Answer: (c) \(\frac{1}{2}\)

Question 16.
Kirchhoffs first and second laws for electrical circuits are consequences of:
(a) conservation of energy
(b) conservation of electrical charge and energy respectively
(c) conservation of electric charge
(d) neither conservation of energy nor electric charge

Answer

Answer: (b) conservation of electrical charge and energy respectively

Question 17.
A potential difference of 10 V is applied across a conductance of 2 S. The current in the conductor will be :
(a) 20 A
(b) 5 A
(c) 0.2 A
(d) None of these

Answer

Answer: (a) 20 A

Question 18.
The length and radius of an electric resistance of a certain wire are doubled simultaneously, then the:
(a) resistance will be doubled and specific resistance will be halved
(b) resistance will be halved and specific resistance will remain uncharged
(c) resistance will be halved and the specific resistance will be doubled
(d) resistance and specific resistance will both remain uncharged

Answer

Answer: (b) resistance will be halved and specific resistance will remain uncharged

Question 19.
A galvanometer acting as a volt meter will have with its coil.
(a) a high resistance in parallel
(b) a high resistance in series
(c) a low resistance in parallel
(d) a low resistance in series

Answer

Answer: (b) a high resistance in series

Question 20.
When three identical bulbs of 60 W, 200 V rating are connected in series to a 200 V supply, the power drawn by them will be:
(a) 20 W
(b) 60 W
(c) 180 W
(d) 10 W

Answer

Answer: (a) 20 W

Question 21.
n resistances, each of R Ω, are connected in parallel gives an equivalent resistance of R Ω. If these resistances were , connected in series, the combination would have a resistance in Ω is equal to
(a) n²R
(b) R/n²
(c) R/n
(d) nR

Answer

Answer: (a) n²R

Question 22.
In questions 135, w hen the wires are connected in series, the heat produced in the thinner wire is H₁ and that in the thicker wire is H₂. Then :
(a) H₁ = H₂
(b)H₁ < H₂
(c) H₁ > H₂
(d) H₁ > H₂

Answer

Answer: (c) H₁ > H₂

Question 23.
The resistance of a human body is about:
(a) 12 Ω
(b) 120 Ω
(c) 12 KΩ
(d) 120 MΩ

Answer

Answer: (c) 12 KΩ

Question 24.
Why is the Wheatstone bridge more accurate than other methods of measuring resistances: ‘
(a) It is a null method
(b) It is based on Kirchhoffs laws
(c) It has four resistances
(d) It does not involve ohm’s law

Answer

Answer: (a) It is a null method

Question 25.
A 5 A fuse wire can with stand a maximum power of 1 W in circuit. The resistance of the fuse wire is:
(a) 0.2 Ω
(b) 5 Ω
(c) 0.4 Ω
(d) 0.04 Ω

Answer

Answer: (d) 0.04 Ω

CBSE Class 12 Physics - MCQ and Online Tests - Unit 2 - Electrostatic Potential and Capacitance

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CBSE Class 12 Physics – MCQ and Online Tests – Unit 2 – Electrostatic Potential and Capacitance

Question 1.
In which of the following forms is the energy stored in a capacitor?
(a) Charge
(b) Potential
(c) Capacitance
(d) Electric field

Answer

Answer: (d) Electric field

Question 2.
The capacitance of a capacitor will decrease if we introduce a slab of:
(a) copper
(b) aluminium
(c) zinc
(d) None of these

Answer

Answer: (d) None of these

Question 3.
Twenty seven drops of mercury are charged simultaneously to the same potential of 10 volts. What will be potential if all the charged drops are made to combine to form one large drop ?
(a) 180 V
(b) 90 V
(c) 120 V
(d) 45 V

Answer

Answer: (b) 90 V

Question 4.
Two capacitors of capacitance 6 µF and 4 µF are put in series across a 120 V battery. What is the potential difference across the 4 µF capacitor ?
(a) 72 V
(b) 60 V
(c) 48 V
(d) zero

Answer

Answer: (a) 72 V

Question 5.
The P.E. of an electric dipole is maximum when it makes an angle θ with electric field. The value of θ is :
(a) \(\frac{π}{2}\)
(b) π
(c) zero
(d) \(\frac{3π}{2}\)

Answer

Answer: (b) π

Question 6.
An electron initially at rest is accelerated through a potential difference of one volt. The energy gained by electron is:
(a) 1 J
(b) 1.6 × 10^-19 J
(c) 10^-19 J
(d) None of these

Answer

Answer: (b) 1.6 × 10^-19 J

Question 7.
The dimensions of fall of potential per unit distance are given by:
(a) [MLT^-3 A^-1]
(b) [ML²T^-2A^-1]
(c) [ML²T^-2A^-3]
(d) [MLT^-2A^-2]

Answer

Answer: (c) [ML²T^-2A^-3]

Question 8.
If a +ve charge is moved from low to high potential region,
the electric potential energy:
(a) decreases
(b) increases
(c) remain the same
(d) may increase or decrease

Answer

Answer: (b) increases

Question 9.
Two conducting spheres of radii r₁ and r₂ are equally charged. The ratio of their potential is
(a) (r₁/r₂)²
(b) (r₁r₂)²
(c)(r₁/r₂)
(d) (r₂/r₁)

Answer

Answer: (b) (r₁r₂)²

Question 10.
A bird sitting on a high power line:
(a) gets killed instantly
(b) gets a mild shock
(c) gets a fatal shock
(d) is not affected practically

Answer

Answer: (d) is not affected practically

Question 11.
Choose the SI unit of electric potential energy :
(a) Joule
(b) Coulomb
(c) Netwon per coulomb
(d) Erg

Answer

Answer: (a) Joule

Question 12.
The capacitance of earth, viewed as a spherical conductor of radius 6408 km is:
(a) 1420 µF
(b) 712 µF
(c) 680 µF
(d) 540 µF

Answer

Answer: (b) 712 µF

Question 13.
Which of the following is blocked by a capacitor ?
(a) A.C.
(b) D.C.
(c) Both A.C. and D.C.
(d) Neither A.C. nor D. C

Answer

Answer: (b) D.C.

Question 14.
The amount of work required to increase the distance between -6µC and 4µC from 6 cm to 18 cm will be :
(a) 1.8 J
(b) 2.4 J
(c) 1.8 µJ
(d) 2.4 µJ

Answer

Answer: (b) 2.4 J

Question 15.
A capacitor is connected to a cell of emf E having some internal resistance r, the potential across the:
(a) cell is < E
(b) cell is E
(b) cell is > E
(d) capacitor is E

Answer

Answer: (b) cell is E

Question 16.
Two capacitors of 3 µF and 6 µF are connected in series with a battery of P.d. 12 V. The P.d. across 3µF and 6µF
capacitors respectively will be :
(a) 8 V, 4 V
(b) 6 V, 6 V
(c) 4 V, 8 V
(d) 9 V, 3 V

Answer

Answer: (a) 8 V, 4 V

Question 17.
Two copper spheres of the same radius, one solid and the other hollow, are charged to the same potential. Which will have more charge?
(a) Solid sphere
(b) Hollow sphere
(c) Both will have an equal charge
(d) None of these

Answer

Answer: (c) Both will have an equal charge

Question 18.
An electric charge of 425 f µC is removed from a fully charged capacitor of capacitance 8.5µF. Its potential will be lowered by:
(a) 75 V
(b) 100 V
(c) 85 V
(d) 50 V

Answer

Answer: (b) 100 V

Question 19.
The electric potential of earth is taken as:
(a) zero
(b) infinity
(c) unity
(d) None of these

Answer

Answer: (a) zero

Question 20.
A dielectric is placed in between the two parallel plates of a capacitor as shown in the figure. The dielectric constant of the dielectric being K. If the initial capacity is C, then the new capacity will be:

(a) (K + l).C
(b) K.C
(c) \(\frac{(K+1)}{2}\) C
(d) (k – l) C

Answer

Answer: (c) \(\frac{(K+1)}{2}\) C

Question 21.
Minimum number of capacitor of 2µF each required to obtain a capacitance of 5µF will be:
(a) 4
(b) 3
(c) 5
(d) 6

Answer

Answer: (a) 4

Question 22.
A capacitor is connected across a battery and the plate separation of capacitor is increased without removing the battery, then:
(a) capacitance will increase
(b) charge stored will increase
(c) energy stored will decrease
(d) potential difference will increase

Answer

Answer: (c) energy stored will decrease

Question 23.
When a dielectric slab is introduced between the plates of a parallel plate capacitor which remains connected to a battery then charge on the plates relative to earlier charge is :
(a) more
(b) less
(c) less or may be more
(d) same

Answer

Answer: (a) more

Ans. (a)

Question 24.
The surface density of charge is measure:
(a) Cm^-1
(b) Cm^-2
(c) Cm^-3
(d) JC^-1

Answer

Answer: (b) Cm^-2

Question 25.
A polythene piece rubbed with wool is found to have a negative charge of 6.4 × 10^-9c. How many electrons have been transferred during the process?
(a) 4 × 10¹²
(b) 4 × 10¹¹
(c) 4 × 10¹⁰
(d) None of these

Answer

Answer: (c) 4 × 10¹⁰

Question 26.
In the above question:
(a) no electrons are transferred
(b) electrons are transferred from wool to x polythene
(c) electrons are transferred from polythene to wool
(d) nothing can be decided

Answer

Answer: (b) electrons are transferred from wool to x polythene

Question 27.
In previous question, mass transferred to polythene is:
(a) 3.64 × 10²⁰ kg
(b) 4 × 10^-28 kg
(c) 4 × 10¹⁰ kg
(d) None of these

Answer

Answer: (a) 3.64 × 10²⁰ kg

Question 28.
What is the number of electrons in 100 g water?
(a) 3.35 × 10²⁴
(b) 3.35 × 10²⁵
(c) 6.02 × 10²³
(d) None of these

Answer

Answer: (a) 3.35 × 10²⁴

Question 29.
Choose the vector physical quantity:
(a) Electric flux
(b) Electric potential
(c) Electric potential energy
(d) Electric intensity

Answer

Answer: (d) Electric intensity

Question 30.
A uniform electric field of 10 NC^-1 exists in the vertically downward direction. What is the increase in the electric potential asonegoes up through a height of 300 cm ?
(a) 15 V
(b) 30 V
(c) 45V
(d) None of these

Answer

Answer: (b) 30 V

CBSE Class 12 Physics - MCQ and Online Tests - Unit 1 - Electric Charges and Fields

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CBSE Class 12 Physics – MCQ and Online Tests – Unit 1 – Electric Charges and Fields

Question 1.
Electric field in a cavity of metal:
(a) depends upon the surroundings
(b) depends upon the size of cavity
(c) is always zero
(d) is not necessarily zero

Answer

Answer: (d) is not necessarily zero

Question 2.
1 coulomb is equal to:
(a) 3 × 10⁹ e.s.u.
(b) \(\frac{1}{3}\) × 10⁹ e.s.u.
(c) 3 × 10¹⁰ e.s.u.
(d) \(\frac{1}{3}\) × 10¹⁰ e.s.u.

Answer

Answer: (a) 3 × 10⁹ e.s.u.

Question 3.
A parrot comes and sits on a bare high power line. It will:
(a) experience a mild shock ‘
(b) experience a strong shock.
(c) get killed instantaneously
(d) not be affected practically

Answer

Answer: (d) not be affected practically

Question 4.
Three charges + 3q + q and Q are placed on a st. line with equal separation. In order to maket the net force on q to be zero, the value of Q will be :
(a) +3q
(b) +2q
(c) -3q
(d) -4q

Answer

Answer: (a) +3q

Question 5.
Each of the two point charges are doubled and their distance is halved. Force of interaction becomes p times, w here p is :
(a) 1
(b) 4
(c) \(\frac{1}{16}\)
(d) 16

Answer

Answer: (d) 16

Question 6.
The dimensional representation of cu will be :
(a) [MLT⁴ A²]
(b) [M^-1L^-3T⁴A²]
(c)[ML^-2T ]
(d) None of these

Answer

Answer: (b) [M^-1L^-3T⁴A²]

Question 7.
When placed in a uniform field, a dipole experiences:
(a) a net force
(b) a torque
(c) both a net force and torque
(d) neither a net force nor a torque

Answer

Answer: (b) a torque

Question 8.
The SI units of electric dipole moment are:
(a) C
(b) Cm^-1
(c) Cm
(d) Nm^-1

Answer

Answer: (c) Cm

Question 9.
The dielectric constant of a metal is:
(a) 0
(b) 1
(c) ∞
(d) -1

Answer

Answer: (c) ∞

Question 10.
If sphere of bad conductor is given charge then it is distributed on:
(a) surface
(b) inside the surface
(c) only inside the surface
(d) None

Answer

Answer: (d) None

Question 11.
Which one of the following is the unit of electric field?
(a) Coulomb
(b) Newton
(c) Volt
(d) N/C

Answer

Answer: (d) N/C

Question 12.
If two conducting sphere are connected after charging separately then:
(a) Electrostatic energy sphere energy will remain conserved
(b) Electrostatic energy charges remains conserved
(c) Electrostatic energy energy and charge remains conserved
(d) None

Answer

Answer: (b) Electrostatic energy charges remains conserved

Question 13.
The number of electron-taken out from a body to produce 1 coulomb of charge will be :
(a) 6.25 × 10¹⁸
(b) 625 × 10¹⁸
(c) 6.023 × 10²³
(d) None

Answer

Answer: (a) 6.25 × 10¹⁸

Question 14.
The work done in rotating an electric dipole in an electric field:
(a) W = ME (1 – cos θ)
(b) W = ME tan θ
(c)W = ME sec θ
(d) None

Answer

Answer: (a) W = ME (1 – cos θ)

Question 15.
In non-uniform electric field, electric dipole experiences:
(a) torque only
(b) torque as well as net force
(c) force only
(d) None of these

Answer

Answer: (b) torque as well as net force

Question 16.
Coulomb’s law in vector form can be written as
\(\vec{F} \) = (\(\frac{1}{4πε_n}\)) (\(\frac{q_1q_2}{r^2}\))\(\vec{r} \)
where ε₀ is the permitivity of free space. The SI units of ε₀ will be:
(a) N^-1m^-2C^-2
(b) Nm^-2C²
(c) N^-1m^-2C⁹.
(d) Nm^-2C²

Answer

Answer: (c) N^-1m^-2C⁹

Question 17.
The belt of a Vande Graaf generator gets charge by :
(a) corona discharge
(b) induction
(c) electrification
(d) None of these

Answer

Answer: (a) corona discharge

Question 18.
An electron is sent in an electric field of magnitude 9.1 × 10⁶NC^-1. The acceleration produced in it is :
(a) 1.6 ms^-2
(b) 1.6 × 10¹⁸ms^-2
(c) 3.2 × 10¹⁸ms^-2
(d) 0.8 × 10¹⁸ ms^-2

Answer

Answer: (b) 1.6 × 10¹⁸ms^-2

Question 19.
Two point charges +8q and -2q are located at ,v = O and ,v = L respectively. The location of a point on the .v-axis at which the net electric field due to these two point charges b is zero :
(a) 4L
(b) 8L
(c) L/4
(d) 2L

Answer

Answer: (d) 2L

Question 20.
A semicircular arc of radius r is charged uniformly and the charge per unit length is λ. The electric field at the centre is:
(a) \(\frac{λ}{2λε_0r^2}\)
(b) \(\frac{λ}{4πε_0r}\)
(c) \(\frac{λ^2}{2πε_0r}\)
(d) \(\frac{λ}{2πε_0r}\)

Answer

Answer: (b) \(\frac{λ}{4πε_0r}\)

Question 21.
The graph drawn between V are r for a non-conducting charged solid sphere of radius R for r < R will be :
(a) straight line
(b) parabola
(c) hyperbola
(d) None of these

Answer

Answer: (d) None of these

Question 22.
If an electric dipole is kept in a uniform electric field then resultant electric force on it is :
(a) always zero
(b) never zero
(c) depend upon capacity of dipole
(d) None

Answer

Answer: (a) always zero

Question 23.
Corona discharge takes place:
(a) at the surface of a conductor
(b) near the sharp points of a conductor
(c) outside the conductor
(d) at the centre of the conductor

Answer

Answer: (b) near the sharp points of a conductor

Question 24.
A soap bubble is given a negative charge, then its radius:
(a) increases
(b) decreases
(c) remains unchanged
(d) may increase or decrease

Answer

Answer: (a) increases

Question 25.
When a dipole of moment \(\vec{p} \) is placed in uniform electric field \(\vec{E} \), then the torque acting on the dipole is:
(a) \(\vec{τ} \) = \(\vec{p} \).\(\vec{E} \)
(b) \(\vec{τ} \) = \(\vec{P} \) + \(\vec{E} \)
(c) \(\vec{τ} \) = \(\vec{p} \) + \(\vec{E} \)
(d ) \(\vec{τ} \) = \(\vec{p} \) – \(\vec{E} \)

Answer

Answer: (c) \(\vec{τ} \) = \(\vec{p} \) + \(\vec{E} \)

CBSE Class 12 Maths - MCQ and Online Tests - Unit 13 - Probability

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CBSE Class 12 Maths – MCQ and Online Tests – Unit 13 – Probability

Question 1.
If P (a) = \(\frac{3}{8}\), P(b) = \(\frac{1}{2}\) and P(A∩B) = \(\frac{1}{4}\) then P(\(\frac{A’}{B’}\)) =
(a) \(\frac{1}{4}\)
(b) \(\frac{1}{3}\)
(c) \(\frac{3}{4}\)
(d) \(\frac{3}{8}\)

Answer

Answer: (b) \(\frac{1}{3}\)

Question 2.
If A and B are two events such that P(a) ≠ 0 and P(\(\frac{B}{A}\)) = 1, then
(a) B ⊂ A
(b) B = φ
(c) A ⊂ B
(d) A ∩ B = φ

Answer

Answer: (c) A ⊂ B

Question 3.
If A and B are any two events such that P(a) + P(b) – P(A∩B) = P(a) then
(a) P(\(\frac{B}{A}\)) = 1
(b) P(\(\frac{B}{A}\)) = 0
(c) P(\(\frac{A}{B}\)) = 1
(d) P(\(\frac{A}{B}\)) = 0

Answer

Answer: (c) P(\(\frac{A}{B}\)) = 1

Question 4.
If A and B are events such that P (A∪B) = \(\frac{3}{4}\). P(A∩B) = \(\frac{1}{4}\), P(a) = \(\frac{2}{3}\) then P(AB) is
(a) \(\frac{3}{8}\)
(b) \(\frac{5}{8}\)
(c) \(\frac{5}{12}\)
(d) \(\frac{1}{4}\)

Answer

Answer: (b) \(\frac{5}{8}\)

Question 5.
If one card is drawn out of 52 playing cards, the probability that it is an dice is
(a) \(\frac{1}{26}\)
(b) \(\frac{1}{13}\)
(c) \(\frac{1}{52}\)
(d) \(\frac{1}{4}\)

Answer

Answer: (b) \(\frac{1}{13}\)

Question 6.
The chance of getting a doublet with 2 dice is
(a) \(\frac{2}{3}\)
(b) \(\frac{1}{6}\)
(c) \(\frac{5}{6}\)
(d) \(\frac{5}{36}\)

Answer

Answer: (b) \(\frac{1}{6}\)

Question 7.
Two number are chosen, one by one without replacement from the set of number A = {1, 2, 3, 4, 5, 6} then the probability that minimum value of two number chosen is less than 4 is
(a) \(\frac{14}{15}\)
(b) \(\frac{1}{15}\)
(c) \(\frac{1}{5}\)
(d) \(\frac{8}{5}\)

Answer

Answer: (b) \(\frac{1}{15}\)

Question 8.
If P(x) = \(\frac{2}{15}\); y = 1, 2, 3, 4, 5, 0 otherwise then P|x = 1 or 2| is
(a) \(\frac{1}{15}\)
(b) \(\frac{2}{15}\)
(c) \(\frac{1}{5}\)
(d) None of these

Answer

Answer: (c) \(\frac{1}{5}\)

Question 9.
The probability of an event is \(\frac{3}{7}\). Then odd against the event is
(a) 4 : 3
(b) 7 : 3
(c) 3 : 7
(d) 3 : 4

Answer

Answer: (a) 4 : 3

Question 10.
Five horse are in a race. Mr. A select two of the horses at random and best on them. The probability that Mr. A select the winning horses is
(a) \(\frac{4}{5}\)
(b) \(\frac{3}{5}\)
(c) \(\frac{1}{5}\)
(d) \(\frac{2}{5}\)

Answer

Answer: (d) \(\frac{2}{5}\)

Question 11.
If A and B are two independent events, then
(a) P(A∩B) = P(a) × P(b)
(b) P(AB) = 1 – P(A’) P(B’)
(c) P(AB) = 1 + P (A’) P(B’) P(A’)
(d) P (AB) = \(\frac{P(A’)}{P(B’)}\)

Answer

Answer: (a) P(A∩B) = P(a) × P(b)

Question 12.
The probability of India w inning a test match against. West Indies is \(\frac{1}{2}\). Assuming independence from match to match the probability that in a match series India second win occurs at the third test is
(a) \(\frac{1}{6}\)
(b) \(\frac{1}{4}\)
(c) \(\frac{1}{2}\)
(d) \(\frac{2}{3}\)

Answer

Answer: (b) \(\frac{1}{4}\)

Question 13.
P(A∩B) = \(\frac{3}{8}\), P(b) = \(\frac{1}{2}\) and P(a) = \(\frac{1}{4}\) then P(\(\frac{B’}{A’}\)) =
(a) \(\frac{3}{5}\)
(b) \(\frac{5}{8}\)
(c) \(\frac{3}{8}\)
(d) \(\frac{5}{6}\)

Answer

Answer: (d) \(\frac{5}{6}\)

Question 14.
Three distinct numbers.are selected from First 100 natural numbers. The probability divisible by 2 and 3 is
(a) \(\frac{9}{25}\)
(b) \(\frac{4}{35}\)
(c) \(\frac{4}{55}\)
(d) \(\frac{4}{1155}\)

Answer

Answer: (d) \(\frac{4}{1155}\)

Question 15.
A pair of dice are rolled. The probability of obtaining an even prime number on each die is
(a) \(\frac{1}{36}\)
(b) \(\frac{1}{12}\)
(c) \(\frac{1}{6}\)
(d) 0

Answer

Answer: (a) \(\frac{1}{36}\)

Question 16.
If P(a) = \(\frac{3}{8}\), P(b) = \(\frac{1}{3}\) and P(A∩B) = — then P (A’ ∩B’)
(a) \(\frac{13}{24}\)
(b) \(\frac{13}{8}\)
(c) \(\frac{13}{9}\)
(d) \(\frac{13}{4}\)

Answer

Answer: (a) \(\frac{13}{24}\)

Question 17.
The probability that A speaks truth is \(\frac{4}{5}\) while this probability for B is \(\frac{3}{4}\). The probability that they contradict each others when asked to speak ana fact is
(a) \(\frac{7}{20}\)
(b) \(\frac{1}{5}\)
(c) \(\frac{3}{20}\)
(d) \(\frac{4}{5}\)

Answer

Answer: (d) \(\frac{4}{5}\)

Question 18.
If P(a) = \(\frac{7}{10}\) P(b) = \(\frac{7}{10}\) and P(A∪B) = \(\frac{7}{10}\) then P (B|A) + P(A|B) equals
(a) \(\frac{1}{4}\)
(b) \(\frac{1}{3}\)
(c) \(\frac{5}{12}\)
(d) \(\frac{7}{12}\)

Answer

Answer: (d) \(\frac{7}{12}\)

Question 19.
Two dice are tossed once. The probability of getting an even number at the first dice ora total of 8 is
(a) \(\frac{1}{36}\)
(b) \(\frac{3}{36}\)
(c) \(\frac{11}{36}\)
(d) \(\frac{5}{9}\)

Answer

Answer: (d) \(\frac{5}{9}\)

Question 20.
A pair of dice are rolled. The probability of obtaining an even prime number on each dice is
(a) \(\frac{1}{36}\)
(b) \(\frac{1}{12}\)
(c) \(\frac{1}{6}\)
(d) 0

Answer

Answer: (a) \(\frac{1}{36}\)

Question 21.
If A, B are two events associated with same random experiment such that P(a) = 0.4, P(b) = 0.8 and P(B/A) = 0.6 then P(A/B) is
(a) 0.3
(b) 0.4
(c) 0.5
(d) 0.6

Answer

Answer: (a) 0.3

Question 22.
If P(a) = \(\frac{3}{8}\), P(b) = \(\frac{5}{8}\), P(A∪B) = \(\frac{3}{4}\) then p(\(\frac{B}{A}\)) is
(a) \(\frac{3}{47}\)
(b) \(\frac{5}{49}\)
(c) \(\frac{2}{3}\)
(d) \(\frac{1}{4}\)

Answer

Answer: (c) \(\frac{2}{3}\)

Question 23.
If A and B are two events such that P(a) ≠ 0 and P(\(\frac{B}{A}\)) = 1 then
(a) P(\(\frac{A}{B}\)) = 1
(b) P(\(\frac{B}{A}\)) = 1
(c) P(\(\frac{A}{B}\)) = 0
(d) P(\(\frac{B}{A}\)) = 0

Answer

Answer: (b) P(\(\frac{B}{A}\)) = 1

Question 24.
An urn contain’s balls of which 3 are red, 4 are blue and 2 are green, 3 balls are drawn at random without replacement from the urn. The probability that the 3 balls haye different colours is
(a) \(\frac{1}{3}\)
(b) \(\frac{2}{7}\)
(c) \(\frac{1}{21}\)
(d) \(\frac{2}{23}\)

Answer

Answer: (b) \(\frac{2}{7}\)

Question 25.
An experiment has 10 equally likely outcomes. Let A and B be two non-empty events of the experiment. A consists 4 outcomes, the number of outcomes that B must have so that A and B are independent is
(a) 2, 4 or 8
(b) 36 or 9
(c) 4 or 8
(d) 5 or 10

Answer

Answer: (d) 5 or 10

Question 26.
The mean and the variance of binomial distribution are 4 and 2, respectively. Then the probability of 2 success
(a) \(\frac{128}{256}\)
(b) \(\frac{219}{256}\)
(c) \(\frac{7}{64}\)
(d) \(\frac{28}{256}\)

Answer

Answer: (c) \(\frac{7}{64}\)

Question 27.
If P(a) = \(\frac{4}{5}\) and P(A∩B) = \(\frac{7}{10}\), then P(B/A) is equal
(a) \(\frac{1}{10}\)
(b) \(\frac{1}{8}\)
(c) \(\frac{7}{8}\)
(d) \(\frac{17}{20}\)

Answer

Answer: (d) \(\frac{17}{20}\)

Question 28.
If P(A∩B) = \(\frac{7}{10}\) and P(b) = \(\frac{17}{20}\), then P(A|B) equals
(a) \(\frac{14}{17}\)
(b) \(\frac{17}{20}\)
(c) \(\frac{7}{8}\)
(d) \(\frac{1}{8}\)

Answer

Answer: (a) \(\frac{14}{17}\)

Question 29.
If A and B are two independent events with P(a) = \(\frac{3}{5}\) and P (b) = \(\frac{4}{9}\), then P (A’∩B’) equals
(a) \(\frac{4}{15}\)
(b) \(\frac{8}{15}\)
(c) \(\frac{1}{3}\)
(d) \(\frac{2}{9}\)

Answer

Answer: (d) \(\frac{2}{9}\)

Question 30.
Let A and B two event such that P(a) = \(\frac{3}{8}\), P(b) = \(\frac{5}{8}\) and P(A∪B) = \(\frac{3}{4}\). Then P(A|B).P(A’|B) is equal to
(a) \(\frac{2}{5}\)
(b) \(\frac{3}{8}\)
(c) \(\frac{3}{20}\)
(d) \(\frac{6}{25}\)
Ans. (d)

Answer

Answer: (d) \(\frac{6}{25}\)

CBSE Class 12 Physics – MCQ and Online Tests – Unit 8 – Electromagnetic Waves

CBSE Class 12 Physics – MCQ and Online Tests – Unit 8 – Electromagnetic Waves

CBSE Class 12 Physics – MCQ and Online Tests – Unit 7- Alternating Current

CBSE Class 12 Physics – MCQ and Online Tests – Unit 7- Alternating Current

CBSE Class 12 Physics – MCQ and Online Tests – Unit 6 – Electromagnetic Induction

CBSE Class 12 Physics – MCQ and Online Tests – Unit 6 – Electromagnetic Induction

CBSE Class 12 Physics – MCQ and Online Tests – Unit 5 – Magnetism and Matter

CBSE Class 12 Physics – MCQ and Online Tests – Unit 5 – Magnetism and Matter

CBSE Class 12 Physics – MCQ and Online Tests – Unit 4 – Moving Charges and Magnetism

CBSE Class 12 Physics – MCQ and Online Tests – Unit 4 – Moving Charges and Magnetism

CBSE Class 12 Physics – MCQ and Online Tests – Unit 3 – Current Electricity

CBSE Class 12 Physics – MCQ and Online Tests – Unit 3 – Current Electricity

CBSE Class 12 Physics – MCQ and Online Tests – Unit 2 – Electrostatic Potential and Capacitance

CBSE Class 12 Physics – MCQ and Online Tests – Unit 2 – Electrostatic Potential and Capacitance

CBSE Class 12 Physics – MCQ and Online Tests – Unit 1 – Electric Charges and Fields

CBSE Class 12 Physics – MCQ and Online Tests – Unit 1 – Electric Charges and Fields

CBSE Class 12 Maths – MCQ and Online Tests – Unit 13 – Probability

CBSE Class 12 Maths – MCQ and Online Tests – Unit 13 – Probability

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