The purpose of a rheostat is: A. To increase the magnitude of current only B. To decrease the magnitude of current only C. To increase or decrease the magnitude of current only D. None of these
Hint:In electrical circuits, a rheostat is an electrical device which is used to change overall resistance of a circuit without changing any other effects in the circuit and in terms of its construction it’s very similar to the potentiometer.
Complete answer: Let us first understand the working of a rheostat in brief. A rheostat is also known as a variable resistor where we can change the resistance of the circuit and its generally used for controlling the amount of current flowing in the circuit. It’s constructed as two terminals where one terminal is fixed and the other one can move between its two ends.
This moving terminal can be chosen in a desired way to change the resistance of the circuit and when it’s chosen in a way such that resistance is large, it decreases the current in the circuit and when it’s chosen in a way such that resistance is low then current in the circuit is increased. So, a rheostat can increase as well as decrease the current.
Hence, the correct option is C.
Note: It should be remembered that the wires which are used to make a rheostat is generally one which has a constant or negligible change in its resistivity over a wide range of temperature and these wires are such as constantan and manganin.