Question 1
FThe Figure shows a Sankey diagram for the electric motor in a food mixer.
Figure
a.[1]
Calculate the value of X.
b.[2]
Use the equation: efficiency=useful output energy transferinput energy transfer\text{efficiency} = \dfrac{\text{useful output energy transfer}}{\text{input energy transfer}}efficiency=input energy transferuseful output energy transfer
Calculate the efficiency of the motor.
c.[2]
The motor gets hot when it is used.
Explain why.
7.2 Power and efficiency Questions
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.