Displacement Current

Conduction Current	Displacement Current
It arises due to the fixed charges.	It arises due to the change in electric field.
Conduction current obeys ohm's law.	Displacement current does not obey ohm's law.
Conduction current is the actual current.	Displacement current is the apparent current produced by time varying electric field.

Consider a capacitor and outside the plates of the capacitor there is conduction current I_C. Area between the plates i.e. inside the capacitor there is displacement current I_d. Physical behavior of displacement current is same as that of induction current.

For Static electric fields,

I_d = 0

For time varying electric fields,

I_d ≠ 0

There can be some scenarios where there will be only conduction current and in some case there will be only displacement current.

Ø Outside the capacitor there is only conduction current and no displacement current.

Ø Inside the capacitor there is only displacement current and no conduction current.

But there can be some scenario where both conduction as well as displacement current is present i.e.

I = I_C + I_d

Applying modified Ampere-Maxwell law to calculate magnetic field at the same point of the capacitor considering different amperial loop, the result will be same.

Ampere – Maxwell law: Consequences

Case 1: Magnetic field is given as

∫dl = μ₀ I_c

∫dl =

Case 2 : Magnetic field is given as

∫dl = μ₀ I_d

∫dl =

Ø The value of B is same in both cases.

Ø Total current should be the same.

Time varying electric field generates magnetic field given by (Ampere-Maxwell law)

Ø Consider 1^st step up there is electric field between the plates and this electric field is varying with time.

Ø As a result there is displacement current and this displacement current gives rise to magnetic field.

Time varying magnetic field generates electric field given by (Faraday-Lenz law)

Ø Therefore if there is electric field changing with time it generates magnetic field and if there is magnetic field changing with time it generates electric field.

Ø Electromagnetic waves are based on the above conclusion.