Question

A source of electromotive force (emf) is
A. Cell
B. Battery
C. Generator
D. All of these

Answer 1

Hint:An electromotive force is considered as the terminal potential difference of a source when there is no current drawn by the circuit. It can also be considered as the maximum voltage that a source can have without any loss.

Complete answer:
An electromotive force is defined as the energy that causes the current to flow in any circuit or conductor. Also, an electromotive force is considered as the terminal potential difference of a source when there is no current drawn by the circuit. It is abbreviated as Emf.

Now, we know that emf is induced when there is a flow of charge. Since, there is a flow of charge in the cell, battery and generator. Therefore, we can say that am emf can be induced in all the three sources.Therefore, the source of emf is cell, battery and generator.

Hence, option D is correct.

Note:An electromotive force can be calculated by the device potentiometer. A potential is known as a series resistor which is used to provide a controlled voltage supply to a circuit. It is necessary to find the emf of the circuit so that we find the maximum efficiency of the battery.