A coulomb is a very large unit of charge and is therefore very hard to obtain. However, fairly large currents of several amperes (coulombs/second) are very common. How is this possible?
2007-12-01 03:20:49 · 5 answers · asked by on_the_bb 2 in Science & Mathematics ➔ Physics
Electrons are small, in fact they are point like. In one second it will not be difficult to get 10 to the 19 electons past a spot. This is what an Ampere is.
2007-12-01 03:29:17 · answer #1 · answered by Brian 6 · 0⤊ 0⤋
Coulomb is a charge of electrical force, it has nothing to do with the physical size of the electron. 6.2 X 10^18 electrons, each with one unit of electron charge, make up a Coulomb. And if one Coulomb's worth of electrons pass through a point on a conductor in 1 second, that's 1 Ampere of current.
Although we know little of the size of an electron, we do know its rest mass m = 9.10956 x 10-31 kg. [See source.] That is, it'd take about N = 10^30 electrons to make a mass M = 1 kg. To put that into perspective, 1 Coulomb of electrons would have a total mass of about 60 X 10^-12 kg. That's pretty small mass even though there are 6.1 X 10^18 of them in that little bit of wire carrying 1 Ampere of current.
Bottom line, when we are talking subatomic size, we are talking really really small. So even 6.1 X 10^18 electrons would have hardly any total mass whatsoever.
2007-12-01 04:47:23 · answer #2 · answered by oldprof 7 · 0⤊ 0⤋
This is not a question of the physics involved. The problem stems from just how much charge a coulomb was decided to be. It could have been one electron charge or two or ten, but for historic reasons it was given the value it has. It would be convenient to work in smaller units because we almost always have to deal with micro or pico or some small number of coulombs, but again for historical reasons we have just left it where it is.
2007-12-01 08:30:34 · answer #3 · answered by mojorisin 3 · 0⤊ 0⤋
Coulomb found experimentally that the force of attraction between unlike charges or of repulsion between like charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them. Thus, force, F varies as ( and not equal to ) qq' / r^2. This means that F = kqq' / r^2. where k is the proportionality constant, the value of which was determined conducting a large number of experiments. Equating dimensions on boths sides, the unit of this constant is NM^2/C^2. If q, q' and r are taken as unity, F = k which gives physical interpretation of k as the force between unit charges kept at a unit distance.
2016-05-27 02:44:21 · answer #4 · answered by renetta 3 · 0⤊ 0⤋
Think of a motorcycle battery as a 12 Farad capacitor rather than a collection of secondary cells.
2007-12-01 03:26:22 · answer #5 · answered by Anonymous · 0⤊ 1⤋