Class 12 Physics Electric Charges and Fields MCQs (Mixed) with Answers
These Class 12 Physics MCQs cover Electric Charges and Fields (Electrostatics), a chapter where many students lose marks due to sign mistakes, direction confusion, and weak basics about field lines. This mixed set is meant for quick, exam-style revision: charging methods, Coulomb’s law idea, superposition, electric field lines, dipoles, and simple conventions like area vector direction. Each question includes the correct answer with a short explanation so you can fix concepts, not just remember options.
MCQs (Mixed Practice)
Question 1
What does the divergence of gold leaves in a gold-leaf electroscope indicate?
A. Presence and approximate amount of charge on the body
B. Temperature of the charged body
C. Mass of the charged body
D. Only the polarity of charge
Correct Answer: A
Explanation: When charge reaches the leaves, they repel and separate. Greater divergence generally means more charge (it doesn’t directly “measure” mass/temperature).
Question 2
According to the principle of superposition, the net force on a charge due to several other charges is:
A. The algebraic sum of the magnitudes of individual forces
B. The vector sum of the forces due to each charge (considered one at a time)
C. Always the force due to the nearest charge only
D. Zero if there are more than two charges
Correct Answer: B
Explanation: Forces are vectors. Add each force vector to get the net force.
Question 3
Three charges $+q$, $+q$, and $-q$ are at the vertices of an equilateral triangle. The vector sum of forces on all three charges (considering the system as a whole) is:
A. Zero
B. Non-zero and along one side
C. Equal to the force on $-q$ only
D. Dependent only on the magnitude of $q$, not its sign
Correct Answer: A
Explanation: Internal forces between charges occur in action–reaction pairs, so the total force on the whole isolated system is zero.
Question 4
Assertion (A): The electric field at a point on the dipole axis is along the dipole moment vector. Reason (R): Electric fields due to $+q$ and $-q$ add along the dipole axis.
A. Both A and R are true and R is the correct explanation of A
B. Both A and R are true but R is not the correct explanation of A
C. A is true but R is false
D. A is false but R is true
Correct Answer: A
Explanation: On the axis, both contributions are along the same line, giving a net field along the dipole moment direction.
Revision Tip: For field-line questions, remember: direction is the direction a positive test charge would move.
Question 5
The solid angle $d\Omega$ subtended by a small area element $dS$ at distance $r$ from a point charge is:
A. $d\Omega = dS,r^2$
B. $d\Omega = \frac{dS}{r^2}$
C. $d\Omega = \frac{r^2}{dS}$
D. $d\Omega = dS,r$
Correct Answer: B
Explanation: Solid angle measures how large an area appears from a point: $d\Omega = \frac{dS}{r^2}$.
Question 6
Which statement about electric field lines of a point charge is correct?
A. Field line density increases with distance from the charge
B. Field line density decreases with distance from the charge
C. Field lines start at negative charges and end at positive charges
D. Field lines form closed loops around a point charge
Correct Answer: B
Explanation: Electric field magnitude for a point charge decreases as $\frac{1}{r^2}$, so line density decreases with distance. Field lines start at positive and end at negative.
Question 7
For a closed surface, the area vector $\vec{dA}$ at each small element is taken along:
A. The inward normal
B. The outward normal
C. The direction of electric field always
D. The direction of current flow
Correct Answer: B
Explanation: By convention, $\vec{dA}$ for a closed surface points outward.
Question 8
Assertion (A): Electric charge is a scalar quantity. Reason (R): Charges add algebraically.
A. Both A and R are true and R is the correct explanation of A
B. Both A and R are true but R is not the correct explanation of A
C. A is true but R is false
D. A is false but R is true
Correct Answer: A
Explanation: Charge has magnitude but no direction, and addition of charges follows ordinary algebra.
Revision Tip: In charging by rubbing, electrons transfer. Protons don’t move between bodies in ordinary situations.
Question 9
Why does a nylon comb get electrified on combing dry hair but a metal spoon usually does not?
A. Nylon is a conductor; metal is an insulator
B. Nylon is an insulator; metal is a conductor
C. Metal has no free electrons
D. Nylon creates new charges
Correct Answer: B
Explanation: Nylon holds charge because it is insulating. A metal spoon quickly allows charge to flow through your body to earth.
Question 10
Quantisation of charge means:
A. Charge can have any fractional value
B. Charge on any body is an integral multiple of $e$
C. Charge is continuous at microscopic level
D. Only positive charge is possible
Correct Answer: B
Explanation: $q = ne$, where $n$ is an integer and $e$ is the elementary charge.
Prefer level-wise practice? Try: Class 12 Physics Electric Charges and Fields MCQs (Difficulty-wise).
If you’re revising for a test, attempt the set once without help, then redo only the questions you got wrong after reading the explanations.