From David Smith
Patrick Wise asks: “How do I know whether or not the light in my fridge goes
out when I close the door?”
(19 May, p 55).
The low-tech answer from a long-in-the-tooth physicist is: leave the door
closed for an hour. Open the door and quickly feel the light bulb. Assuming it’s
a conventional tungsten filament light source—and I’ve never seen anything
else used in a domestic fridge—if it’s cold, the light was off prior to
the door being opened. If it’s warm, then the switch is faulty.
No doubt there are many other approaches, depending on your discipline. An
electrical engineer, for example, would measure the current consumption to see
if it drops when the door is closed. An occupational hygienist would measure
light levels inside with the door closed. A statistician could prove that there
is a 99.95 per cent chance that the switch does work correctly every time. A
philosopher might argue that it doesn’t matter anyway. And an anarchist would
deliberately leave the door open . . .
Tamworth, Staffordshire
