NEET 2025 · PhysicsAmpere-Maxwell lawPrevious Year Question
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 the displacement current is
- A.Non-zero everywhere with maximum at the imaginary cylindrical surface connecting the peripheries of the plates✓
- B.Zero between the plates and non-zero outside
- C.Zero at all places
- D.Constant between the plates and zero outside the plates
Correct Answer
(A) Non-zero everywhere with maximum at the imaginary cylindrical surface connecting the peripheries of the plates
Solution & Explanation
Answer: (A) Non-zero everywhere with maximum at the imaginary cylindrical surface connecting the peripheries of the plates. The displacement current produces a magnetic field that circles the axis. Inside (r < R), B ∝ r (grows with radius); outside (r > R), B ∝ 1/r (falls off). Hence B is maximum at the edge r = R (the cylindrical surface joining the plate rims) and non-zero both inside and outside.
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