# CBSEtips.in

## Thursday, 28 January 2021

### 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

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 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: (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: (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: (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

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

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

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

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

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

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

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

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: (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: (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

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

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

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

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: (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

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

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: (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

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

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