A 600W immersion heater is placed in 1.0kg of water initially at 20∘C. The heater is left on continuously for 4.0min. Assume no energy is lost to the surroundings except as noted.
The specific heat capacity of liquid water is c=4.186×103Jkg−1∘C−1.
(a) Determine the total electrical energy delivered by the heater during the 4.0min interval.
(b) Assuming all of this energy is transferred to the water, calculate the theoretical final temperature of the water.
(c) In an actual experiment, the measured final temperature is 40∘C. Calculate the percentage of the electrical energy that was effectively used to raise the water’s temperature, and discuss one plausible physical reason why the efficiency is less than 100%. (No numerical justification of the reason is required.)