An electrical appliance is protected by a fuse containing a thin metal wire.
The wire in the fuse melts when a charge flow of 3.5 C3.5\text{ C}3.5 C passes through it in a time of 0.50 s0.50\text{ s}0.50 s. Calculate the current in the wire when it melts. Use the equation:
current=charge flowtime \text{current} = \frac{\text{charge flow}}{\text{time}} current=timecharge flowThe mass of the fuse wire is 0.024 g0.024\text{ g}0.024 g and the specific latent heat of fusion of the wire is 85,000 J/kg85{,}000\text{ J/kg}85,000 J/kg. Calculate the thermal energy needed to melt the wire. Use the equation:
energy=mass×specific latent heat \text{energy} = \text{mass} \times \text{specific latent heat} energy=mass×specific latent heatThe fuse transfers some energy to its surroundings as it heats up and melts. How does transferring energy to the surroundings affect the total energy that must be supplied to melt the fuse?
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.