Not too long ago houses were protected from excessive currents by fuses rather than circuit breakers. sometimes a fuse blew out and a replacement wasn't at hand. because a copper penny happens to have almost the same diameter as a fuse, some people replaced the fuse with a penny. unfortunately, a penny never blows out, no matter how large the current, and the use of pennies in fu se boxes caused many house fires. make the appropriate measurements on a penn y, then calcul ate the resistance between the two faces of a solid-copper penny. (modern pennies have the same dimensions, but are made of zinc with a copper coating.)