Displacement current \( (i_d) = \displaystyle\frac{\varepsilon_o\,d\phi_E}{dt} \).
Where symbols have their usual meanings.
Which of the following options gives correct equation for displacement current?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \( i_d = A\,\varepsilon_o\,\displaystyle\frac{dE}{dt} \)
The displacement current arises from a changing electric flux. For a uniform field \( E \) normal to an area \( A \) (as between the plates of a capacitor), the electric flux is \( \phi_E = EA \). The area stays fixed, so
\( \displaystyle i_d = \varepsilon_o\,\frac{d(EA)}{dt} = A\,\varepsilon_o\,\frac{dE}{dt} \)