Question bank/NEET UG/Physics

NEET UGPhysicsModerateNEET 2025

A parallel plate capacitor made of circular plates is being charged such that the surface charge density on its plates is increasing at a constant rate with time. The magnetic field arising due to displacement current is:

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Sol. Let the surface charge density be σ=qA\sigma = \frac{q}{A}

Given dσdt\frac{d\sigma}{dt} = constant

∴ddt(qA)\therefore \frac{d}{dt}\left( \frac{q}{A} \right) = constant ⇒IA=i\Rightarrow \frac{I}{A} = i = constant

It means displacement current is constant.

This system will act like a cylindrical wire.

The graph of magnetic field (B) vs r is
<image_1>

Source: geekyrakshit/indian-exam-questions / neet2025-code45

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