Question

Lumped heat capacity in a solid body is used when,

• A. when internal resistance is more than 10% of surface resistance
• B. when internal resistance is 63.2% of surface
• C. when external resistance is equal to 10% of surface resistance
• D. when internal resistance is less than 10% of surface resistance

Answer 1

The correct option is D when internal resistance is less than 10% of surface resistance

when internal resistance (due to conduction) is less than 10% of surface (convction) resistance.
i.e. Bi < 0.1
$\frac{\text{Internal resistance}}{\text{Surface resistance}}<0.1$
i.e internal resistance < 10% of surface resistance