Consider an electric motor with a shaft power output of 20 kW and an efficiency of 88 percent. Determine the rate at which the motor dissipates heat to the room it is in when the motor operates at full load. In winter, this room is normally heated by a 2-kW resistance heater. Determine if it is necessary to turn the heater on when the motor runs at full load. My question is how can i find heat dissipate ? 1. The problem statement, all variables and given/known data power output = 20 kW efficiency = 0.88 operates at full load power input = 20/0.88 = 22.72 kW 3. The attempt at a solution Method 1 (only inefficiency causes heat) : (1-0.88)* (22.72) = 2.72 kW Method 2 (inefficiency causes heat & energy from shaft movement cause increase in air kinetic energy which in the end become thermal energy) = power input = 22.72 kW Method 3 (from solution manual which i don't understand) = (1-0.88) * power output = 0.12 * 20 = 2.4 kW Which one should i use and why ?