Question

The rheostat differs from a potentiometer in the respect that if;
A) rheostat has large number of turns
B) rheostat offers larger number of tappings
C) rheostat has lower wattage rating
D) rheostat has higher wattage rating

Answer 1

The resistance can be changed by using rheostat as well as potentiometer and rheostat suitable for high power devices and potentiometer is used for low power devices.

Complete answer:
Potentiometer is a three terminal electrical instrument and used to change the resistance in the circuit and controls the voltage across the circuit and it is suitable for devices which require low power like, joystick, volume control on television, radio, etc. It is a senior type of instrument.
The figure below represents symbol of potentiometer:

Rheostat is a two terminal electrical instrument and used to control current in the circuit. It is also used to adjust the resistance of the circuit and it is suitable for the devices, which requires high power like, fans, television, refrigerator etc. It is a variable resistor type of an instrument.
The figure below represents symbol of rheostat:

Therefore, the rheostat differs from a potentiometer in the respect of wattage rating as the rheostat is suitable for high power devices; it has higher wattage rating as compared to the potentiometer.

Note: The rheostat is connected in a series combination with the circuit while the potentiometer is connected in a parallel combination with the circuit. A potentiometer is composed of graphite while the rheostat is composed of very thin carbon film. A potentiometer can be used as a rheostat, but the reverse is not possible.