Question

In a series LCR circuit the frequency of a 10 V AC voltage source is adjusted in such a fashion that the reactance of the inductor measures 15W and that of the capacitor 11W. If R = 3W, the potential difference across the series combination of L and C will be-

• A. 8 V
• B. 10 V
• C. 22 V
• D. 52 V

Answer 1

Answer: (A)

8 V

Answer 2

Z = $\sqrt{3^{2} + (15–11)^{2}}$ = 5

\ I = $\frac{V}{Z}$= $\frac{10}{5}$= 2 amp

\ V_L = I X_L = 2 × 15 = 30 V

V_C = I X_C = 2 × 11 = 22 V

but V_L & V_C are in opposite phase

Ž net voltage of L & C = 30 – 22 = 8 volt