Resistance

Resistance is the measure of difficulty of passing an electric current through a material (measured in ohms).

If the material is rubber it has a very high resistance.

If the material is copper it has a very low resistance.

To visualise resistance scientists have found that a `250mm` length of graphite pencil should have `1` unit of resistance (`1` ohm)

Graphite pencil used to measure 1 ohm.

NOTE: Don't forget to sharpen both ends

Another way of looking at resistance is to consider the following:

Two tanks of water.

There is less resistance in Tank A and it will empty a lot faster than Tank B.

So too in terms of pipes.

Water flowing through two pipes.

There is less resistance in Pipe A and therefore flow will be a lot faster through it than Pipe B.

Also, there is less resistance in copper than rubber in electron flow:

Electrons travelling through copper and rubber.

Another way of thinking about resistance is hair getting stuck in a pipe.

Water in two baths one with fast flow one with slow flow of water.

Resistance `=` Hair