NEET 2024 Physics Question 39 Solution
Question
A parallel plate capacitor is charged by connecting it to a battery through a resistor. If I is the current in the circuit, then in the gap between the plates:
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A parallel plate capacitor is charged by connecting it to a battery through a resistor. If I is the current in the circuit, then in the gap between the plates:
Circuit current must be continuous across space: Displacement current I_d in the gap EXACTLY equals conduction current I in magnitude and direction!
Between the plates of a parallel plate capacitor, no actual physical charge carriers cross the vacuum or dielectric gap. However, as the capacitor charges with current I = dQ/dt, the charge Q on the plates increases, causing a time-varying electric field E and electric flux Φ_E between the plates:
Maxwell defined the displacement current I_d as the rate of change of electric flux scaled by permittivity ε₀:
As positive charge accumulates on the positive plate and negative charge on the negative plate, the electric field E points from positive to negative plate. Since E is increasing, dE/dt and therefore the displacement current density J_d = ε₀ dE/dt is directed from positive to negative plate, continuing seamlessly in the same direction as the conduction current I entering the capacitor.
Diagnose every choice: Know exactly why the right option works and why distractors fail.
Opposite direction would violate conservation of charge and loop continuity.
Displacement current is exactly equal to I, not greater.
Classical Ampère misconception before Maxwell’s correction.
Fundamental Ampère-Maxwell law: I_d = I with identical forward direction.
Many candidates pick Option (1) believing displacement current opposes conduction current.
"Displacement current between capacitor plates has magnitude identically equal to the conduction current in the connecting wires and flows in the same direction."
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