A-LevelPhysicsWork, energy and power9702/12 · May/June 2011 · Q181 Mark
An electric motor produces 120 W of useful mechanical output power. The efficiency of the motor is 60%. Which row is correct?
Aelectrical power input/W: 72, waste heat power output/W: 48
Belectrical power input/W: 192, waste heat power output/W: 72
Celectrical power input/W: 200, waste heat power output/W: 72
Delectrical power input/W: 200, waste heat power output/W: 80
✓ Correct answer
D: electrical power input/W: 200, waste heat power output/W: 80
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