Question

Electromagnetic induction is not used in
A. Transformer
B. Room heater
C. AC generator
D. Choke coil

Answer 1

Electromagnetic induction is the process of the production of current and electromotive force because of the relative motion of the coils and the magnet which causes the change in magnetic flux and hence voltage is produced. Heat in a system is generally produced due to current and resistor of the circuit.

Complete answer:
Current is induced in a coil when there is change in magnetic flux and hence electromotive force is generated between the coil and the magnet. This was first proposed by Faraday and hence is known as the Faraday’s law of electromagnetic induction. Relative motion is needed between the coil and the magnet and hence electromotive force and current are generated.

Now, in a transformer, there are primary coils as well as secondary coils, and the voltage in the secondary coils is generated due to the phenomenon of electromagnetic induction. In AC generators, the voltage is produced because of electromagnetic induction as there is a coil and a magnet whose relative motion constantly generates a change in flux which causes the production of electromagnetic induction.

Choke coils are electromagnetic inductors that block higher-frequency alternating current (AC) in an electrical circuit and pass lower-frequency or direct current (DC). In a room heater, the heating effect takes place because of the power generated due to the resistor which is proportional to the current flowing.

Hence option B is the correct answer.

Note: The power produced due to the current and the resistor is given by the formula $H = {I^2}R$ where H is the heat or power produced, while $I$ is the current produced in the circuit and R is the total resistance in the circuit. This heating can sometimes decrease the efficiency of the circuit and also damage the circuit.