A heating element in an electric heater consists of a metal wire that glows red when a current passes through it. The middle of the wire is at a very high temperature, while the ends, connected to the cooler terminal supports on the heater frame, are at a much lower temperature. Which statement is correct?
Thermal energy is conducted along the wire from the middle towards the terminal supports.
The wire radiates electromagnetic energy equally from all parts of its surface.
All of the electrical input energy is transferred by the heater as infrared radiation.
If the potential difference across the wire is doubled, the power output is doubled.
301 exam-style questions on CIE IGCSE Physics 2.3 Transfer of thermal energy, covering 2.3.1a Thermal conductors and thermal insulators, 2.3.1b Explaining thermal conduction, 2.3.2 Convection, 2.3.3a Thermal radiation, 2.3.3b Surface colour and texture, 2.3.3c Rate of emission and absorption of radiation, and 2.3.4 Consequences of thermal energy transfer. Each one has a worked solution and a mark scheme showing where the marks go.