A student investigates how the thickness of insulation around a beaker affects how quickly hot water in the beaker cools.
The student records the temperature drop of the water in 10 minutes for different numbers of layers of insulation.
Which variable should the student keep the same?
The number of layers of insulation
The temperature drop in 101010 minutes
The thickness of the insulation used
The volume of hot water in the beaker
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.