An electric motor has an input power of 250 W. In 2.0 minutes, the motor lifts a load and increases its gravitational store by 18 kJ.
What is the efficiency of the motor?
0.600.600.60
363636
0.000 600.000\,600.00060
1.71.71.7
50 exam-style questions on OCR GCSE Physics 7.2 Power and efficiency, covering 7.2.1 Dissipation of energy, 7.2.2 Energy transfers in domestic devices, 7.2.3 Power ratings of domestic appliances, 7.2.4 Efficiency of energy transfers, 7.2.5 Ways to increase efficiency, 7.2.6 Reducing unwanted energy transfers, and 7.2.7 Thermal conductivity and the cooling of buildings. Each one has a worked solution and a mark scheme showing where the marks go.