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

Hint: Resistors are used to reduce the current in a circuit by a precise amount. Current passing through the resistor is limited due to the presence of voltage across it. And it converts electrical energy into heat. But a choke coil does not limit the current by its resistance. It works based on induction methods.

Complete answer:
Choke coils are used to reduce the current in an electrical circuit. We use it as a substitute for resistance in AC circuits. When current is passing through a resistor, it will heat up. So while using resistance as a current controlling device, it wastes huge amounts of electrical energy in the form of heat, due to which power loss is high and current is also reduced. But choke works based on the principle of Inductance. Hence, the power factor of the choke coil is very small. It absorbs very less power compared to resistance. The only loss of energy is due to hysteresis in the iron core, which is very less compared to resistance.

So, the correct answer is “Option B”.

Note:
A choke coil is an inductor which can be used to block higher-frequency while passing direct current (DC current) and lower-frequencies of alternating current (AC) in a circuit. Its reactance limits the amount of AC passing through the circuit. With the eddy currents produced in a choke coil it helps in reducing the current in the circuit due to self induction. Choke is used only in AC circuits. Since its inductive reactance is zero for DC current, it cannot be used in DC circuits.