Question

A choke is preferred to a resistance for limiting current in AC circuit because

• A. choke is cheap
• B. there is no wastage of power
• C. choke is compact in size
• D. choke is a good absorber of heat

Answer 1

Answer: (B)

In an AC circuit, the coil of high inductance and negligible resistance used to control current, is called the choke coil. The power factor of such a coil is given by $\cos o|=\frac{R}{\sqrt{R^2+{\omega }^2{L}^2}}$ $\approx \frac{R}{\omega L}$ $(asR<<\omega L)$ As $R<<\omega L,coso|$ is very small. Thus, the power absorbed by the coil is very small. The only loss of energy is due to hysteresis in the iron core, which is much less than the loss of energy in the resistance that can also reduce the current if placed instead of the choke coil.