2025
- Two point charges q1 and q2 are placed 1 m apart in vacuum. The force between them is 9 N. If each charge is doubled and distance halved, what is the new force?
Concept: Coulomb’s law, inverse square law.
2024
- A point charge +Q is placed at the center of a spherical shell of radius R. What is the electric field at the surface of the shell?
Concept: Electric field inside a conductor and due to spherical symmetry. - Work done in moving a charge q from point A to point B in an electric field is independent of the path. True or False?
Concept: Electric potential and conservative nature of electrostatic field.
2023
- Two identical charges repel each other with force F at a distance r. If one charge is doubled and the other halved, the force becomes?
Concept: Coulomb’s law application.
2022
- A uniform electric field exists between two parallel plates separated by distance d. A particle of charge q is released from rest. What is the acceleration of the particle?
Concept: Electric field, force, and Newton’s second law.
2021
- The potential at a point P due to a point charge Q is 100 V. If a charge q = 2 μC is placed at P, what is the potential energy of the charge?
Concept: Electric potential energy.
2020
- Electric field at the midpoint of a line joining two equal charges Q separated by distance 2a is?
Concept: Superposition principle in electrostatics.
2019
- A charge of 4 μC is at the origin. Find the work done in moving a 2 μC charge from x = 1 m to x = 2 m along the x-axis.
Concept: Electric potential difference and work.
2018
- A small charge q is placed at a distance r from a large charge Q. Find the force on q.
Concept: Coulomb’s law, vector nature of forces.
2017
- Two point charges +Q and −Q are separated by distance 2a. Find the electric field at a point on the perpendicular bisector.
Concept: Electric field due to dipole.
2016
- Electric potential at the center of a uniformly charged ring of radius R is?
Concept: Superposition principle and symmetry.
2015
- A sphere of radius R carries charge Q uniformly over its surface. Electric field outside the sphere at distance r from the center is?
Concept: Gauss’s law for spherical charge distribution.
2014
- Two identical charges separated by distance r experience a repulsive force F. If distance is doubled, what is the new force?
Concept: Coulomb’s law, inverse square relation.
2013
- Work done in bringing two point charges from infinity to separation r is?
Concept: Electrostatic potential energy.
Answer
2025
Q: Two charges q1 and q2 at 1 m exert 9 N force. If each charge is doubled and distance halved, new force?
Solution:
- Original: F=kr2q1q2=9 N
- New: F′=k(0.5)2(2q1)(q2/2)=k0.25q1q2=36 N
Answer: 36 N
2024
Q1: Point charge +Q at center of spherical shell. Electric field at surface?
Solution: By Gauss’s law: Electric field outside a shell behaves as if charge is concentrated at center. At surface, E=4πϵ01R2Q
Answer: E=4πϵ0R2Q
Q2: Work done moving q from A to B independent of path?
Solution: Electrostatic field is conservative → work depends only on potential difference.
Answer: True
2023
Q: Two identical charges repel with F at distance r. One doubled, other halved → force?
Solution: F′=kr2(2Q)(Q/2)=kr2Q2=F
Answer: F
2022
Q: Particle of charge q in uniform field between plates. Acceleration?
Solution: F=qE, a=F/m=qE/m
Answer: a = qE/m
2021
Q: Potential at P = 100 V. Charge q = 2 μC placed → potential energy?
Solution: U=qV=2×10−6×100=2×10−4 J
Answer: 0.2 mJ
2020
Q: Electric field at midpoint between two equal charges Q at distance 2a?
Solution: Midpoint → fields equal magnitude, opposite directions → vector addition → E = 0
Answer: 0
2019
Q: Charge 4 μC at origin. Work to move 2 μC from x=1 to x=2 m?
Solution: W=qΔV=q(r2kQ−r1kQ)=2×10−6(29×109⋅4×10−6−19×109⋅4×10−6)
- W = -18 × 10^-3 J
Answer: -0.018 J
2018
Q: Small charge q at distance r from Q → force?
Solution: Coulomb’s law: F=kr2Qq
2017
Q: Two charges +Q, −Q separated by 2a. Field at perpendicular bisector?
Solution: Dipole → E=4πϵ01(a2+y2)3/22Qa
2016
Q: Electric potential at center of uniformly charged ring of radius R?
Solution: V=kRQ (all points equidistant)
2015
Q: Sphere radius R, charge Q uniformly. Field at r>R?
Solution: E=4πϵ01r2Q (Gauss’s law)
2014
Q: Two charges at distance r → F. If distance doubled, new force?
Solution: F′=F(2r)2r2=F/4
2013
Q: Work bringing two charges from infinity to r?
Solution: W=krq1q2