Electric Charges & Fields

Previous Years' CBSE Board Questions

1.2 Electric Charges

MCQ

1 A negatively charged object X is repelled by another charged object Y. However an object Z is attracted to object Y. Which of the following is the most possibility for the object Z?

1. Positively charged only.

7 object W on object X is F. Then the magnitude of the

force exerted by object W on Z is

1. F/7 (b) F/5 (c) F/3 (d) F/2 (Term I 2021-22) (Ap)

1. Negatively charged only.
2. Neutral or positively charged.
3. Neutral or negatively charged.

(Term I 2021-22) (II

1.4 Basic Properties of Electric Charge

MCQ

2 In an experiment three microscopic latex spheres are sprayed into a chamber and became charged with charges +3e, +5e and -3e respectively. All the three spheres came in contact simultaneously for a moment and got separated. Which one of the following are possible values for the final charge on the spheres?

Four objects W, X, Y and Z each

with charge +q are held fixed at

four points of a square of side d as

shown in the figure. Objects X and

Z are on the midpoints of the sides

of the square. The electrostatic

force exerted by

VSA (1 mark)

Two identical conducting balls A and B have charges

-Q and +3Q respectively. They are brought in contact

with each other and then separated by a distance d

apart. Find the nature of the Coulomb force between

them.

(2019) R

Two equal balls having equal positive charge 'q'

coulombs are suspended by two insulating strings of

equal length. What would be the effect on the force

when a plastic sheet is inserted between the two?

1. +5e, -4e, +5e(b) +6e, +6e, -7e (Al 2014)
2. -4e, +3.5e, +5.5e (d) +5e, -8e, +7e (Term I 2021-22) [U

1. An object has charge of 1 C and gains <math>5.0 \times 10^{18}</math> electrons. The net charge on the object becomes
2. -0.80 C (b) <math>+0.80 C</math>
3. + 1.80 C (d) +0.20 C

(Term I 2021-22) (R)

1.5 Coulomb's Law

MCQ

1. Three charges <math>q_1</math> –q and <math>q_0</math> are placed as shown in figure. The magnitude of the net force on the charge go at point O is

k=-1

<math>\neg q</math>

90 0

1. 0
2. 2kqq

1. (d)

(Term I 2021-22)

LA (5 marks)

Two identical point charges, q each, are kept

2 m apart in air. A third point charge Q of unknown

magnitude and sign is placed on the line joining the

charges such that the system remains in equilibrium.

Find the position and nature of q.

(3/5, Delhi 2019) [Mi]

1.7 Electric Field

MCQ

Question No. 9 is Assertion (A) and Reason (R) type

questions. Given below are the two statements labelled

as Assertion (A) and Reason (R). Select the most

appropriate answer from the options given below.

1. Assertion (A): A negative charge in an electric field moves along the direction of the electric field. Reason (R): On a negative charge a force acts in the direction of the electric field.
2. Both (A) and (R) are true and (R) is correct explanation of (A).
3. Both (A) and (R) are true, and (R) is not correct explanation of (A).
4. (A) is true, but (R) is false.
5. (A) is false and (R) is also false.

(Term I 2021-2)

SA II (3 marks)

(Term I 2021-22) (R

A particle of charge 2 μC and mass 1.6 g is moving with a velocity <math>4ims^{-1}</math>. At <math>t = 0</math> the particle enters in a region having an electric field E (in N C-1) = 80i+60j. Find the velocity of the particle at <math>t = 5 s</math>. (2/3, 2020)

(5 marks)

Two point charges of +1 μC and +4 μC are kept 30 cm apart. How far from the +1 µC charge on the line joining the two charges, will the net electric field be zero? (2/5, 2020)

A thin circular ring of radius r is charged uniformly so that its linear charge density becomes λ. Derive an expression for the electric field at a point P at a distance x from it along the axis of the ring. Hence, prove that at large distances <math>(x >> r)</math>, the ring behaves

(a) <math>a^4c</math> (b) <math>\frac{1}{3}a^3c</math> (c) <math>\frac{1}{3}a^4c</math> (d) 0

SAI (2 marks)

21. An electric field along the x-axis is given by

<math>\vec{E} = 100 \hat{i} \text{ N/C for } x > 0 \text{ and } \vec{E} = -100 \hat{i} \text{ N/C for } x < 0.</math>

A right circular cylinder of length 20 cm and radius

5 cm lies parallel to the x-axis, with its centre at the

origin and one face at <math>x = +10</math> cm, the other face at

<math>x = -10</math> cm. Calculate the net outward flux through

the cylinder. (AI 2019C) (i) Given a uniform electric field <math>\vec{E}=5\times10^3\,\hat{i}\,\text{N/C}</math>. Find