Chapter Exam

Chapter-1 Electric Charges and Fields — Online MCQ Test

Q: What is the SI unit of electric charge?

Answer: B. Coulomb — Coulomb (C) is the SI unit of electric charge, named after Charles-Augustin de Coulomb.

Q: 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:

Answer: B. E = kQr/R³ — Using Gauss's law with spherical symmetry, E(r) = kQr/R³ inside a uniformly charged sphere.

Q: 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?

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.

PHYSICS · CLASS 12 SECOND PUC · Karnataka State Board

Practice Chapter-1 Electric Charges and Fields with a free chapter-wise online MCQ test for Karnataka State Board CLASS 12 SECOND PUC PHYSICS. 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.

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Chapter-1 Electric Charges and Fields — Important Questions & Answers (FAQ)

Frequently asked questions from Karnataka State Board CLASS 12 SECOND PUC PHYSICS — Chapter-1 Electric Charges and Fields, with answers and explanations. These are sample questions; the exam has its own separate question set.

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'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.

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).

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.

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.