Q. A refrigerator absorbs $2000\ cals$ of heat from ice trays. If the coefficient of performance is 4, then work done by the motor is
A) 2100 J
B) 4200 J
C) 8400 J
D) 500 J
Explanation
(a) $Q_{2} = 2000\ cal.\ \ As\ COP = \frac{Q_{2}}{W}$
$\therefore\ 4 = 2000/W$
$W = 500\ cal = 500 \times 4.2 = 2100\ J$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.