Define displacement current.

Hint :Recall the concepts of electromagnetism and the equations given by Maxwell. Changing magnetic fields give rise to an electric field while changing electric fields also give rise to magnetic fields. Use this concept to understand what displacement current is.

Complete Step By Step Answer:
Displacement current can be explained easily with the help of a capacitor. Consider a capacitor, we know the region between the plates of a capacitor is insulated and charges do not flow from one plate to another that is there no conduction current, so the current present there is called the displacement current. Here, due to changing electric field applied, displacement current is generated due to time varying electric field.
Displacement current is a phenomenon which occurs in electromagnetism and it is the current in a circuit due to time varying electric fields.
The concept of displacement current was first introduced by Maxwell. And it is expressed as,
 $ {i_d} = {\varepsilon _o}\dfrac{{d{\phi _E}}}{{dt}} $ ,
where $ {\varepsilon _o} $ is the permittivity of free space and $ d{\phi _E} $ is the change of electric flux in the time interval $ dt $ .

Note :
Maxwell showed that there are two types of current; one is conduction current and the other is displacement current. Conduction current occurs due to the flow of charges in a circuit, while in case of displacement current there is no actual flow of charge. After the concept of displacement current was established, Maxwell added the term displacement current in Ampere’s circuital law as,
 $ \oint {\overrightarrow B \cdot d\overrightarrow l = {\mu _o}{i_c} + {\mu _0}{\varepsilon _o}} \dfrac{{d{\phi _E}}}{{dt}} $ ,
where $ {i_c} $ is the conduction current and $ {i_d} = {\varepsilon _o}\dfrac{{d{\phi _E}}}{{dt}} $ is the displacement current. This equation is known as Ampere-Maxwell law.