Question

If we decrease the frequency of the applied A.C. with a purely capacitive load, do (1) the amplitude of $V_c$ and (2) amplitude of $I_c$ increase, decrease of remain the same.

• A. (1) increase (2) same
• B. (1) same (2) increase
• C. (1) same (2) decrease
• D. (1) decrease (2) same

Answer 1

Answer: (C)

(1) same (2) decrease

Amplitude of $V_c$ is independent of the frequency of A.C. source. So amplitude of $V_c$ will remain same on changing the frequency.
Amplitude of $I_c=\frac{V_c}{X_C}=\frac{V_c}{1/wC}=wC{V}_c$
So amplitude of $I_c$ will decrease on decreasing the frequency of applied A.C.