when I touch cold metal and feel it’s cold, is this because
a) My nerves sense cold
b) I feel the warmth being sapped from my skin by the metal
or
c) a & b are exactly the same thing
My money’s on c, but I’m not sure.
Any takers?
jb
Loss of heat = cooling, so C.
The answer is ©, with qualifications.
Your nerves detect whether your skin is cold, so they give you the sensation of cold if you touch something which “saps” the heat away as you suggested in (b). Metal is a good heat conductor so it will sap the heat away efficiently (provided that it is actually colder than your skin, of course!) A cube of expanded polystyrene on the other hand won’t feel very cold to the touch even if you’ve just taken it out of the freezer.
An interesting aside is that the level of temperature which your nerves treat as “cold” varies according to their recent temperature history. Try this experiment - take three bowls and fill one with cold tap water, one with hot tap water and one with warm tap water. Put one hand in the hot, one hand in the cold and hold them there a minute. Then take them out and put them both in the warm water. The result is quite bizarre!