for this essay I investigated Ohms Law. I investigated the effect that the length and the thickness of wire had on the resistance.

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Investigating Resistance

Electricity is the flow of electrons. Resistance is the slowing of this flow. Resistance will increase when there are more electrons for the current to collide with. It will also increase when the electrons are moving at a high speed. There are five main factors that affect resistance. These are

i.Length of wire

ii.Temperature of wire

iii.Voltage that is used to push current around circuit.

iv.Thickness of piece of wire.


i.If the length of the wire is increased, the resistance will increase. If the length of the wire is decreased, the resistance will decrease. This is because if the wire is increased from 10cm to 20cm the electrons will have more wire particles to collide with.

I.E ?

10 cm 20 cm

ii.As with all solids, liquids and gases, if the wire is heated, the particles will gain more energy and will move faster. Due to this the electrons will collide with the wire particles more frequently than if the wire was cool.

I.E ?

Cool Wire Heated Wire

iii.If the voltage in the wire is increased, the heat of the wire will increase. As with ii. the particles will move faster thus creating more collisions between the electricity particles and the particles in the wire.

I.E ?

2V 4V

iv.The thicker the piece of wire, the less resistance there will be. This is because the electrons have more space to move in. Therefore, there will be fewer collisions between particles and this will reduce the resistance.

I.E ?

26 SWG 24 SWG

v.As some materials are better conductors than others, this will obviously affect the resistance. This is why gold plugs are preferable in stereo systems.


To investigate what affects resistance. I have chosen to investigate length at 5cm intervals and thickness. I have chosen 24 SWG, 26 SWG and 28SWG (with 24 SWG being the thickest wire and 28 SWG being the thinnest).


Ohms Law states: "The current flowing through a metal wire is proportional to the potential difference across it (providing the temperature remains constant).

I predict that as the length is increased, the resistance will increase proportionally. This is due to collisions between electrons and wire particles. The resistance will become greater as there are more particles in a 10cm wire than in a 5cm wire, thus more particles for the current to collide, therefore greater resistance.


5 CM 10 CM

I also predict that the resistance in the 28 SWG wire will be greater than that in the 24 SWG wire. Because the 28 SWG wire is thinner than the 24 SWG wire, There is less room for the particles to move in the 28 SWG wire than in the 24 SWG wire. As there is less room for the particles to move, collisions will happen more frequently. This will raise the resistance. The values of resistance in the 26 SWG wire will be in between the values of the resistance for the 24 SWG wire and the 28 SWG wire as the value of the thickness of it is between the values of the thickness' of the other two wires.


28 SWG 26 SWG 24 SWG

Equipment List

12V Power Pack

5 Connecting Wires

Test Wires

Crocodile Clips



Diagram (pre-test and experiment) Shown on next page

Fair Test

For each wire I am only going to change the length of the wire. Everything else (the power pack, voltage, ammeter, voltmeter, connecting wires and crocodile clips) will remain the same to stop the internal resistance in the circuit from changing.


We carried out a pre-test to determine what conditions would be best to carry out our experiment under. Our pre-test went wrong (our results were extremely flawed) because we were using faulty equipment but we were still able to determine that 4V was the best voltage to use and that testing lengths from 0cm to 100cm with 5cm intervals would be better as we would get more precise results than we would if we took results at 10cm intervals

Pre-Test Method

Step 1 Set...
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