Because there are a great many electrons involved. Quantum tunneling happens to a few electrons at a time. An electrical circuit running a 5 milliamps involves 3 × 10^16 electrons per second. A few electrons one way or the other doesn't make much of a difference. There is a very small loss, and you get a few electrons in the wrong place, but the circuit isn't sensitive enough to notice.

The microscopic transistors used in microchips are designed to take advantage of quantum tunneling. The semiconductors don't ordinarily conduct electricity, but when they accumulate enough charge, a few electrons can tunnel over. Because the amount of quantum tunneling is predicted by a mathematical formula, they can use it to their advantage to turn each tiny junction into a miniature amplifier. Arranged properly, you can use this to produce electronic calculating circuits.
Source(s):
http://hyperphysics.phy-astr.gsu.edu/HBASE/electric/elefor.html


Permalink | Report