Question

If a device is being operated at a voltage lower than its rated voltage what happens to the power consumed by the device and its internal resistance.

• A. Power consumption increases as internal resistance increases
• B. Power consumption increases and resistance decreases
• C. power consumption and internal resistance remains constant
• D. power consumption decreases and internal resistance remains constant

Answer 1

The correct option is D

power consumption decreases and internal resistance remains constant

If operating voltage of a device is lowered than its rated voltage the power consumed by the device also lowers down because according to the formula
$P=\frac{V^2}{R}$
if value of V is reduced value of $V^2$ is also reduced and since P is directly proportional to V, P also reduces.
In case of resistance R, it is integral property of the material and doesn't changes with either current or voltage but remains constant for a material. Resistance only changes with change in temperature or change in material.