Question

In the circuit shown in the figure, the ac source gives a voltage V = 24cos(2000t). Neglecting source resistance, the voltmeter and ammeter reading will be

• A. 0V, 0.47A
• B. 1.68V, 0.47A
• C. 8.46V, 1.4 A
• D. 5.6V, 1.4 A

Answer 1

The correct option is C 8.46V, 1.4 A

$Z=\sqrt{(R{)}^2+(X_L-X_c{)}^2}$

$R=12\Omega ,X_L=wL=2000\times 5\times {10}^{-3}=10\Omega$

$X_c=\frac{1}{wC}=\frac{1}{2000\times 50\times {10}^{-6}}=10\Omega$ i.e.Z = 10$\Omega$

Maximum current $i_0=\frac{V_0}{Z}=\frac{24}{12}=2A$

Hence $i_{rms}=\frac{2}{\sqrt{2}}=1.4A$

and $V_{rms}=6\times 1.41=8.46$ V