Question

Name the instrument used to control the current in an electric circuit.
(A). Rheostat
(B). Voltmeter
(C). Ammeter
(D). Galvanometer

Answer 1

Hint: The instrument rheostat is a variable resistor that is used to control current. Moreover it is used in circuits to change the resistance of the circuit i.e. it is able to vary the resistance in the circuit without any interruption.

Complete step-by-step answer:
The instrument used to control in an electric circuit is rheostat. The rheostat is an adjustable or variable resistor. It is used to control the electrical resistance of a circuit without interrupting the flow of current. Moreover the rheostat can adjust generator characteristics, dim light and start and control speed of the motors. Rheostat has 3 dimensions but generally it consists of a resistive wire wrapped to form a toroid coil that contains a wiper and the slides along the surface of the coil. The rheostat is most often designed with the ceramic core.
The applications that are most often used in rheostat require high voltage and the current. Therefore the resistances elements can be a metal wire or ribbon, carbon, or a conducting liquid, depending on the application.

Note:There is a difference between resistors and rheostat i-e the both terms are used in a circuit for the same function, to offer resistance to the current flow. The only difference is that in resistors, the resistance value is fixed such as (100 ohm to 200 ohm) whereas in rheostat the resistance value can vary within the range as per requirement such as (1 ohm to 200 ohm).