Question

A 1500W heating element is submerged in 1L of 20°C water. Assuming that container is perfectly insulated, estimate time needed to raise the temperature of the water to 100°C.

Answer 1

Answer:

Amount of heat required to raise temperature of m kg of water by T degrees is given by

Q = C*m*T

Where C is the specific heat of water = 4186 J/kg-K

Here m = 1 kg (1 liter of water has a mass of 1kg)

T = 100 -20 = 80 Deg.

Hence energy required to raise the temperature from 20 deg. to 100 deg. is:

Q = 4186 * 1*80

Q = 334,880 J

We know that Power = Energy/Time,

Therefore Time = Energy/Power = 334880/1500 = 223.25 seconds, or

time = 3 minutes, 43 seconds approx

Hope this helps