• The vanes of a radiometer turn even before the glow from a heating coil is visible.
  • Hold the index card between the heating coil and radiometer to stop the vanes.
  • Do not turn the heating coil on full unless it is at least 30 cm from the radiometer.
        (place heating coil on heat protective surface)
        (place globe 10 cm from filament, set variac between 50-60)
        (check that room lights do not affect radiometer)