Question

If the power factor changes from $\frac{1}{2}\,to\,\frac{1}{4}$ ,then what is the increase in impedance in A.C. ?

• A. 0.2
• B. 0.5
• C. 0.25
• D. 1

Answer 1

Answer: (D)

1

Answer 2

cos $\theta \propto \frac{1}{Z} ; \frac{Z_1}{Z_2} = \frac{cos \, \theta_1}{cos \, \theta_2} = \frac{1/4}{1/2} = \frac{1}{2} \, z_2 = 2 z_1$ Percentage change = $\frac{2 Z_1 - Z_1}{Z_1} \times 100$= 100 %.