# To find out what happens to the resistance of a wire, when you change the length of the wire.

Kira Harman                                                                                                 28/04/2007

Resistance Of Wire.

Aim. To find out what happens to the resistance of a wire, when you change the length of the wire.

Background Information.

A current of electricity is the flow of negatively charged electrons around a circuit.

Close up, the wire and the electrons look like this:

The electrons collide with the atoms as they travel through. We say the atoms ‘oppose’ the flow of electrons. This is called resistance, and the wire gets hotter.

In 1826, Georg Ohm discovered that when a current flows through a metal wire the current and the potential differences are proportional, providing that the temperature remains constant.

The resistance of wire can be calculated using:

Variables.

Temperature increases the resistance as the atoms are getting hotter they are vibrating and moving faster. This makes the atoms and the electrons collide more.

Thickness of wire decreases the resistance, as there is more room for the electrons to travel past the atoms. They don’t collide as much.

Length of wire increases the resistance because the electrons have further to move and more collisions occur. So, if you double the length of wire, you double the resistance. Because the number of atoms and the number of collisions doubles.

Type of wire affects resistance because different types have different atom arrangements. Some have different patterns, and some are arranged so that electrons have an easier path to travel through the atoms.

Fair Test.

To make the experiment fair, I will make sure that the temperature stays the same flowing through the power pack and wire. I ...