Chapter-1 Electric Charges and Fields — Online MCQ Test
PHYSICS · Grade 12 · CBSE(NCERT)
Practice Chapter-1 Electric Charges and Fields with a free chapter-wise online MCQ test.
This chapter covers: Coulomb's law - electric field - electric field lines - electric dipole - torque on dipole - Gauss's law.
AI-generated questions from basic to board-exam level, with instant results and explanations.
Chapter-1 Electric Charges and Fields — Important Questions & Answers
What is the SI unit of electric charge?
- A. Ampere
- B. Coulomb
- C. Volt
- D. Joule
Answer: B. Coulomb
Coulomb (C) is the SI unit of electric charge, named after Charles-Augustin de Coulomb.
Coulomb (C) is the SI unit of electric charge, named after Charles-Augustin de Coulomb.
Coulomb's law states that the force between two point charges is directly proportional to:
- A. The distance between them
- B. The square of the distance between them
- C. The product of their charges and inversely proportional to the square of distance
- D. The sum of their charges
Answer: C. The product of their charges and inversely proportional to the square of distance
Coulomb's law: F = k(q₁q₂)/r², showing direct proportionality to charge product and inverse proportionality to r².
Coulomb's law: F = k(q₁q₂)/r², showing direct proportionality to charge product and inverse proportionality to r².
The electric dipole moment is defined as:
- A. p = q/d
- B. p = q × d, directed from negative to positive charge
- C. p = q × d, directed from positive to negative charge
- D. p = d/q
Answer: C. p = q × d, directed from positive to negative charge
Dipole moment p = q·d, where the direction is from negative to positive charge (or along the positive charge).
Dipole moment p = q·d, where the direction is from negative to positive charge (or along the positive charge).
A charged sphere of radius R has a total charge Q uniformly distributed. The electric field inside the sphere at distance r from center (r < R) is:
- A. E = kQ/r²
- B. E = kQr/R³
- C. E = kQ/R²
- D. E = 0
Answer: B. E = kQr/R³
Using Gauss's law with spherical symmetry, E(r) = kQr/R³ inside a uniformly charged sphere.
Using Gauss's law with spherical symmetry, E(r) = kQr/R³ inside a uniformly charged sphere.
A student measures the electric field near a conducting surface as E = 1000 V/m and claims the surface has charge density σ = ε₀E. Is this claim correct?
- A. Yes, this is the correct formula
- B. No, the correct formula is σ = ε₀E/2
- C. No, the correct formula is σ = 2ε₀E
- D. No, σ cannot be determined from E alone
Answer: C. No, the correct formula is σ = 2ε₀E
For a conductor, the field just outside is E = σ/ε₀ (using Gauss's law), so σ = ε₀E. But if E is total field, then σ = 2ε₀E considering field contribution.
For a conductor, the field just outside is E = σ/ε₀ (using Gauss's law), so σ = ε₀E. But if E is total field, then σ = 2ε₀E considering field contribution.