Question

A refrigerator absorbs $2000cal$ of heat from ice trays. If the coefficient of performance is $4$, then work done by the motor is:

• A. $2100J$
• B. $4200J$
• C. $8400J$
• D. $500J$

Answer 1

The correct option is A $2100J$

A refrigerator absorbs $2000cal$ of heat from ice trays.

$1cal=4.2J$

therefore, $2000cal=8400J$

if coefficient of performance is 4,

efficiency is $\frac{1}{COP}=0.25$

work done by the motor$=\eta \ast E=0.25\ast 8400=2100J$