A space probe's infrared sensor is kept cool using an open-cycle liquid helium cryostat. Over a telemetry monitoring period of 45 minutes45\text{ minutes}45 minutes, a certain mass of liquid helium is vaporised by heat leaking into the vessel and is subsequently vented into space.
Explain how an astrophysicist could use the measured mass of vaporised helium, the monitoring duration, and the standard value for the specific latent heat of vaporisation of helium to estimate the average rate of parasitic heat leak (thermal power) into the cryostat in watts.
37 exam-style questions on AQA GCSE Physics 3.2 Internal energy and energy transfers, covering 3.2.1 Internal energy, 3.2.2 Temperature changes in a system and specific heat capacity, and 3.2.3 Changes of state and specific latent heat. Each one has a worked solution and a mark scheme showing where the marks go.