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:

Non-zero everywhere with maximum at the imaginary cylindrical surface connecting peripheries of the plates

Zero between the plates and non-zero outside

Constant between the plates and zero outside the plates

Moving Charges and Magnetism PYQ — NEET 2025 · Q136 with Solution

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Correct answer: A

Let the surface charge density be $\sigma=\frac{q}{A}$

Given $\frac{d \sigma}{d t}=$ constant

$$\therefore \quad \frac{d}{d t}\left(\frac{q}{A}\right)=\text { constant } \Rightarrow \frac{l}{A} i=\text { constant }$$

It means displacement current is constant.

This system will act like a cylindrical wire.

The graph of magnetic field (B) vs $r$ is