Question

An immersion-heating coil of 1000 W is used to heat 1 kg of water. Calculate the
time in hours required to raise the temperature of water from 20°C to 80°C.
Specific heat of water = 4200 J kg C​

Answer 1

Power of water =2 kw=2000w

Mass of water =200kg

difference in temperature ΔT=70−10=60 o C

Concept

energy required to heat the water = energy given by water in time t=pt

energy required to increase tempeature of water by 60 o C,Q=msΔT

S= specific heat =4200J/kg o C

pt=msΔT

2000×t=200×4200×60

t=25200

or t=25.2×10 ^3 sec.