A torch contains two batteries and a filament lamp.
Name the energy store that decreases when the torch is switched on.
Describe how energy is transferred from the batteries to the surroundings when the torch is switched on.
The filament lamp is replaced by an LED. The LED gives out the same amount of light as the filament lamp.
The batteries now last much longer.
Suggest why.
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.