Electrostatics

JEE Main level, single correct, medium

55 of 311

Question 55 of 311

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R

Assertion A: In electrostatics, a conductor does not store any net charge inside.


Reason R: Inside the capacitor (with no dielectric medium), the free charge carriers, if placed between the plates of capacitor, experience force and drift.


Choose the correct answer from the options given below

Show answer and solution

Answer: (B) Both A and R are true but R is NOT the correct explanation of A

In electrostatics, the electric field inside a conductor is zero. According to Gauss's law, ∮E⃗⋅ds⃗=qinϵ0\oint \vec{E} \cdot d\vec{s} = \dfrac{q_{in}}{\epsilon_0}. Since E⃗=0\vec{E} = 0 everywhere inside the conductor, the net charge enclosed qinq_{in} must be zero. Thus, a conductor does not store any net charge inside its bulk, and any excess charge resides only on its surface. Assertion A is true.

Inside a capacitor with no dielectric medium, a uniform electric field exists between the plates. If free charge carriers are placed in this region, they will experience an electrostatic force
F⃗=qE⃗\vec{F} = q\vec{E} and will drift towards the respective oppositely charged plates. Reason R is true.

Although both statements are factually correct, the behavior of charge carriers in the electric field of a capacitor does not explain why the net charge inside a conductor is zero in electrostatics. Therefore, both A and R are true but R is NOT the correct explanation of A.


Answer: Both A and R are true but R is NOT the correct explanation of A

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