Question Details

A capacitor of capacitance ‘C’, is connected across an ac source of voltage V, given byV=V0 sinωtThe displacement current between the plates of the capacitor, would then be given by :

Options

A

B

C

D

Correct Answer :

I_d = V_0 \omega C \cos \omega t

Solution :

The correct answer is:
Id=V0ωCcosωt

Step-by-Step Explanation:

1. Understanding the relationship between Voltage and Charge:
We are given a capacitor of capacitance C connected across an AC voltage source. The instantaneous voltage across the plates of the capacitor is given by:
V=V0sinωt
The instantaneous charge q on the plates of the capacitor is related to the instantaneous voltage V by the formula:
q=CV
Substituting the expression for V into the charge equation, we get:
q=CV0sinωt

2. Displacement Current in a Capacitor:
According to Maxwell's equation, the displacement current (Id) between the plates of a capacitor is equal to the rate of change of electric flux, which is physically equivalent to the conduction current (Ic) flowing through the connecting wires. Thus, we can find the displacement current by differentiating the charge q with respect to time t:
Id=dqdt

3. Performing the Differentiation:
Now, we differentiate the expression for q with respect to t:
Id=ddt(CV0sinωt)
Since C and V0 are constants, they can be pulled out of the derivative:
Id=CV0ddt(sinωt)
Using the chain rule of differentiation, we know that ddt(sinωt)=ωcosωt. Therefore, we obtain:
Id=V0ωCcosωt
This matches the exact expression shown in the correct option image (image_0.png).

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