Topic: Electromagnetics
The current flowing through a capacitor in an AC circuit is
- A. non-existent
- B. conduction current
- C. displacement current
- D. none of the above
Answer: C. displacement current
Explanation: In a capacitor, there is no direct physical connection between the two plates; instead, an insulator (dielectric) of definite permittivity is placed between them. When an AC field is applied, the changing electric field establishes a path for current known as displacement current. Displacement current is the result of permittivity and exists whenever the electric field changes with time, according to Ampere-Maxwell's law $\nabla \times \vec{H} = J_C + J_D$.