Question

Differentiate between conduction current and displacement current. A capacitor is connected across a source providing time-dependent current. Explain…

Accepted Answer

Conduction current Displacement current --- --- Current in a conductor due to the flow of charge carriers, I c=(d Q)/(d t) Current due to a time-varying electric field and hence electric flux in a region, I D=ε 0 (d φ e)/(d t) Maxwell corrected Ampere's circuital law: the source of a magnetic field is not just the conduction current due to the flow of charges, but also the time rate of change of the electric field. Therefore I=I C+I D I=(d Q)/(d t)+ε 0 (d φ e)/(d t) Outside the capacitor plates, only conduction current flows: I D=0, I=I C While inside the capacitor: I D=I, I C=0

Differentiate between conduction current and displacement current. A capacitor is connected across a source providing time-dependent current. Explain how the total current at an instant is the sum of conduction current and displacement current in the circuit at that instant.

Marking-scheme solution

More from Electromagnetic Waves

Conduction current	Displacement current
Current in a conductor due to the flow of charge carriers, $\displaystyle I_{c}=\dfrac{d Q}{d t}$	Current due to a time-varying electric field and hence electric flux in a region, $\displaystyle I_{D}=\varepsilon_{0} \dfrac{d \phi_{e}}{d t}$