Question

If one places a variable resistance (rheostat) across a voltage source, the voltage across the rheostat is fixed. Then rheostat works as

• A. Current regulator
• B. Voltage regulator
• C. Potentiometer
• D. Voltage and current regulator

Answer 1

The correct option is A Current regulator

According to Ohm's law, the voltage across and current through a resistor are proportional. If one places a variable resistance (rheostat) across a voltage source, the voltage across the rheostat is $fixed$.

By fixing the voltage across the rheostat, the current through becomes inversely proportional to the resistance:

$I=\frac{V}{R}$

Thus we can change the current through varying the rheostat resistance as the voltage (V) is constant.