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Resistance is the measure of a component's tendency to oppose electrical current.

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Resistance is the measure of a component's tendency to oppose electrical current. It happens when travelling electrons in a wire collide with the atoms of the wire. The collisions between the electrons and the atoms cause the electrons to move slower, which in effect causes resistance. So, resistance is how hard it is to move electrons through a wire. Ohm's law states that the current through a conductor is proportional to the p.d. Resistance is the sum of current over voltage.

The diagram below shows that electrons travelling through a current is similar to the flow of water around a set of pipes:


The current is like the flow of the water, and the voltage is like the pressure provided by a pump, which pushes the electrons around the circuit. Resistance is any sort of constriction in the flow, which is what the pressure has to work against. If you turn up the pump (voltage) the flow will increase. If you add more constrictions the flow will decrease.

Electric current will only flow if there are charges which can move freely. Metals contain a sea of electrons (which are negatively charged) and which flow throughout the metal.

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· Crocodile clips

· Ammeter

· Voltmeter

· Power supply

· Meter ruler

· Connecting wires

· sticky tape

· Thin Constantine wire

Safety Issues

The experiment was carried out with great caution. No protective equipment was necessary. The power pack reduced the mains voltage to a safe level for working. The  working area was kept tidy and dry, to avoid short circuiting.


The prediction is that as the length or diameter of the Nichrome wire is increased, the resistance will go up. This is because  

  1. Thinner the wire, the more resistance. This is because the thinner it is the more narrow it is for electrons to go through
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It was a fair test because the voltage was the same for all the experiments. The voltage was four volts. Also, all the same lengths of wire were used, the only variable being the thicknesses and lengths of wire.

For the first factor, length, all three graphs confirm the prediction: all three graphs show that the as the length decreases, so does the resistance. But for the diameter the results were not expected. The wire with the least diameter, (0.19) had the most resistance.

The experiments do not support the original prediction. It is a fact that the diameter affects resistance, so there is obviously an error.


Possible reasons for this error is maybe because of the procedure used. The wire was measured using metre-rulers, and the recording could have been innacurate.

The changes I would make to improve would be to take care in measuring, and to try and use more accurate equipment.

I don't there was enough data to support the prediction. To improve this I would do more experiments. The more results there are, the more likely there'll prove the theory.  

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