# The flowing

### Ropes and Rivers

How much rope goes past each second is the flow. In a river, it's how much water goes past every second. That's quite hard to measure as the water in a river is not travelling at the same speed everywhere. The speed is usually slower at the edges and close to the bottom than in the middle. Fish and ducks know this and do not try to rest in the middle of the river. The rope is easier to think about because it's going at the same speed all the way through.

### In the wire

In a wire you can't see anything, so you need to be careful, just like the river. You cannot even see what's moving inside, but there is something moving and there are electrical meters to measure it. These meters are called ammeters. These measure the flow in amperes. Lots of current is many amperes, a small current only a few amperes.

### Current and movement

For the rope, the flow or current is a number of metres of rope passing through a hand each second. You can see and count it. The stuff that is moving is metres of rope.

For a river, the flow or current is a number of cubic metres of water passing under the bridge each second. Again you can see it, but the current is harder to measure. You cannot just see how fast the water is moving, because the water does not move at just one speed. Th stuff that is moving is cubic metres of water.

For the current or flow inside a wire, the stuff that is moving is something different (not rope, not water), so it has a new name. What moves is electrical charge. Often it's just called charge.