Topic 8: Energy Production For IB Physics HL And SL Students
a) Explain, in terms of the energy of its molecules, why the temperature of a pure substance does not change during melting.
the energy supplied/bonds broken/heat absorbed;
increases potential energy;
no change in kinetic energy (so no change in temperature);
a) State the Stefan-Boltzmann law for a black body.
Power/energy per second emitted proportional to surface area and proportional to the fourth power of absolute temperature/temperature in K; (Note: The Stefan-Boltzmann law was poorly understood with few candidates stating that the absolute temperature is raised to the fourth power.)
b) Deduce that the solar power incident per unit area at distance d from the Sun is given by
solar power is given by 4π σ;
spreads out over sphere of surface area 4π ;
Hence equation is given.