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## Thursday, 28 January 2021

### 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

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 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: (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

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

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]

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

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°

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

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: (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

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

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: (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: (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

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

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

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

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

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: (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: (c) give the direct value of dip

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

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

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

Answer: (a) Lm = $$\frac{5}{6}$$ Lg

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

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