1. The problem statement, all variables and given/known data The heating element in a kettle has a resistance of 10 ohms when it is plugged into a 110V outlet. When heating water, only 75% of the energy produced is actually absorbed by the water. How much heat energy does the water absorb if it takes 4 minutes to boil the water? 2. Relevant equations V = IR P = VI Percent Efficiency = Useful Energy Output / Total Electrical Output 3. The attempt at a solution 1. Finding Energy Produced by Kettle I = V / R I = 11a P = VI =110 x 11 =1210 w 290 400 j (1210 x 60 x 4) of energy produced in 4 minutes 290 400j x 0.75 =217 800j / 3600 =60.5 watt hours is absorb by the water. However, my teacher wrote this on the board: E = V x I x t =110 x 11 x 240 (4 minutes in seconds) =80 2/3 watt hours (output) % Efficiency = Useful Energy Output / Total Electrical Input 75% = 80 2/3 / Total Electrical Energy Input E = 80 2/3 divided by 0.75 E absorbed by water = 108 watt hours His answer confuses me... how could the energy absorbed by the water be more then the energy output? Please help, have a "quest" on this tomorrow.