A food blender is used to make a fruit drink.
The blender is supplied with 12 000 J12\,000\ \text{J}12000 J of energy.
8400 J of this energy is transferred usefully to the kinetic energy store of the blades.
State the equation linking efficiency, useful energy transferred by the device and total energy supplied to the device.
Calculate the efficiency of the blender.
Calculate the energy that is wasted by the blender.
Give one way that the wasted energy is transferred from the blender.
128 exam-style questions on Edexcel GCSE Physics 8.3 Power and efficiency, covering 8.3.1 Power and 8.3.2 Efficiency. Each one has a worked solution and a mark scheme showing where the marks go.