Question

What is the function of a rheostat in the circuit?
(A). It limits the current
(B). It increases the current
(C). It makes the current constant in the circuit
(D). It increases the voltage.

Answer 1

Hint: The rate of flow of charge in a circuit is called current. The ability of a circuit to resist the flow of current through it is called its resistance. Rheostat is a device which controls the resistance of a circuit by introducing or removing resistance elements accordingly whenever required.

Complete answer:

The figure above shows a rheostat. The sliding contact is used to increase or decrease the value of resistance and hence control the flow of current. The connections to the circuit are made through terminal-C and terminal-A or terminal-B.
A rheostat is an adjustable resistor. It is used for adjusting current in a circuit or used in circuits that require variable resistance. The element of resistance can be a metal wire, carbon or a conducting liquid.
A resistor is a device which opposes the flow of current in the circuit.
We can use the rheostat for increasing or decreasing the current in a circuit by changing the resistance of the circuit. Therefore a rheostat helps us in limiting the current in a circuit.

Since rheostat helps us in controlling the flow of current in a circuit, the correct option is (A).

Note:
A potentiometer is also a type of a rheostat. A potentiometer is a device which measures an unknown voltage by balancing with a known potential difference. It contains a wire of certain length and the potential difference is compared against ratios of two lengths. The potential drop per unit length of a potentiometer wire is called its potential gradient.