A parallel plate capacitor made of circular plates is being charged such that the surface charge den

Q: What is NEET?

NEET is a competitive examination conducted in India. This question is from the 2025 NEET Physics paper.

Q: How can I prepare for NEET Physics?

To prepare for NEET Physics, practice previous year questions (PYQs), understand concepts thoroughly, and solve mock tests regularly. This 2025 question covers Electromagnetic Waves topic.

Q: What is the difficulty level of this question?

This NEET 2025 Physics question has a hard difficulty level and is marked as an important question.

Q: Where can I find more NEET previous year questions?

You can find more NEET previous year questions on AspirantMitraa. Browse by subject, topic, year, and difficulty level to practice effectively.

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 displacement current is:

Accepted Answer

Correct Answer: D — Non-zero everywhere with maximum at the imaginary cylindrical surface connecting the peripheries of the platesStep-by-step Solution:Surface charge density σ = q/A; given dσ/dt = constant → d(q/A)/dt = constant → Id/A = constant → displacement current Id = constant.The capacitor with circular plates carrying a constant displacement current behaves exactly like a cylindrical wire carrying that current. The magnetic field from a long straight wire (or cylindrical current):Inside (r : B = µ₀Idr/(2πR²) — increases linearly with r.At the edge (r = R): B = µ₀Id/(2πR) — maximum.Outside (r > R): B = µ₀Id/(2πr) — decreases with r.The maximum magnetic field is at the cylindrical surface connecting the peripheries of the plates (r = R). The field is non-zero everywhere — both inside and outside the capacitor region.Why Option A is wrong: Magnetic field is non-zero between the plates too (it increases with r up to the plate edges).Why Option B is wrong: A constant displacement current does generate a magnetic field — this is the whole point of Maxwell's correction to Ampere's law.Why Option C is wrong: The field between the plates is not constant — it varies linearly with r. It is also non-zero outside (not zero).Key Concepts from Electromagnetic Waves (NCERT Class 12, Chapter 8):Displacement current: Id = ε₀ dΦE/dt. Maxwell introduced this to make Ampere's law consistent.Generalized Ampere's law: ∮B·dl = µ₀(I + Id).The displacement current acts as a source of the magnetic field just like conduction current.Inside the capacitor, B ∝ r (like inside a current-carrying conductor); outside, B ∝ 1/r.

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:

Master NEET with Our Test Series

More Questions from Electromagnetic Waves

Frequently Asked Questions

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:

Master NEET with Our Test Series

More Questions from Electromagnetic Waves

Frequently Asked Questions