Question

A rheostat is used in an electrical circuit

• A. To change the e.m.f
• B. To change the current through the particular instrument
• C. To change the resistance of the circuit
• D. To change the potential difference

Answer 1

The correct option is C

To change the resistance of the circuit

Explanation for the correct option

Option (C)

1. A rheostat is an electric device of variable resistance which is basically used to control the resistance of the circuit to change the current.
2. Diagram

Explanation for incorrect option

Option (A)

1. As we know, the emf force is the potential difference of an open circuit.
2. We can change emf force by rheostat to change the resistance of the rheostat.

Option (B)

1. We can change the circuit current by rheostat to change the resistance of the rheostat.
2. So, changing resistance of rheostat is the cause of current variation, inversely it is not true.

Option (D)

1. If we increase the resistance by the rheostat the voltage across the rheostat will be changed but the potential difference across the circuit will remain the same.

Therefore, a rheostat is used in an electrical circuit to change the resistance of the circuit. So option (C) is correct.