Calorimetry numerical

Question: 6[ref: Selina ICSE class 10]

Find the time taken by a 500 W heater to raise the temperature of 50 kg of material of specific heat capacity 960 J kg-1 K-1, from 18^{o}C to 38^{o}C. Assume that all the heat energy supplied by heater is given to the material.

**Solution**:

Specific heat capacity of material c = 960 J kg-1 K-1

Mass of the material = 50 kg

Change in temperature △T = (38 – 18)^{0} C = 20^{0} C or 20 K

Power of heater P = 500 W

Heat energy required △Q = mc△T

△Q = 50 × 960 × 20

Say, Time taken by a heater to raise the temperature of material = t

Hence, Pt = △Q

t = △Q / P

t = (50 × 960 × 20) / 500

t = 1920 seconds

t = 32 minutes