Question

Wattless current in the circuit is

• A. 3.75 A
• B. 5 A
• C. 2.1 A
• D. zero

Answer 1

The correct option is C 2.1 A

Given,

$R=4\Omega ,X_L=7\Omega ,X_C=4\Omega$

And

$E_m=25v$

$Impedance\left(Z\right)=\sqrt{R^2+{\left(X_L-X_C\right)}^2}$

Substitute all value in above equation

$Impedance\left(Z\right)=\sqrt{4^2+{(7-4)}^2}=\sqrt{16+9}=5\Omega$

Then,

$I_m=\frac{25}{5}=5A$

$sin\theta =\frac{X_L}{Z}=\frac{3}{5}$

$Wattlesscurrent=I_{RMS}\times sin\theta =\frac{5}{\sqrt{2}}\times \frac{3}{5}=\frac{3}{\sqrt{2}}=2.1A$