Investigate 2 Factors Which Affect the Resistance of a Wire

GCSE COURSEWORK

Investigate 2 Factors Which

Affect the Resistance of a Wire

Task:

To find out if the length of wire or the thickness of the wire affects the resistance.

Method:

To try and find out what affect the above variables have on the resistance of a wire I will conduct two experiments. They will both use this layout:

Wire

In the first experiment we will test if the length of wire affects the resistance. To do this we will use 6 different pieces of wire of varying lengths between 5 and 30 centimeters. We will put each piece of wire into the circuit one at a time. We will then find the voltage. Voltage (or Potential Difference) is the difference in the electrical potential of two points, being equal to the electrical energy converted by a unit electric charge moving from one point to another. The SI unit of voltage is the volt (V). We will then measure the current. The current is the flow of electrically charged particles through a conducting circuit due to the presence of a voltage. The current at any point in a circuit is the amount of charge flowing per second. Current carries electrical energy from a power supply, in this experiment it will be a power pack, to the components of the circuit. It may be either direct or alternating current. Once we have found out the voltage and current, we use this formula to find out the resistance:

R=V/I

Resistance is a property of a conductor that restricts the flow of electricity through it. The SI unit of resistance is the ohm. We will do the experiment with each length of wire three times, and then get an average. We will then do exactly the same experiment for the thickness of the wire, except with varying thickness of wire, all the same length.

Safety:

Voltage will be no more than 4v to prevent overheating and melting the wire. The circuit will be kept away from taps and water. We will be standing up ...

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R=V/I

Safety:

Voltage will be no more than 4v to prevent overheating and melting the wire. The circuit will be kept away from taps and water. We will be standing up at all times. Standard classroom rules apply e.g. no running, bags under desks etc.

Apparatus:

Power pack, ammeter, voltmeter, 12 pieces of wire (varying lengths and thickness), proper wires and crocodile clips.

Fair test:

The same power pack, circuit layout, ammeter, voltmeter and wire material will not be changed. There are some things beyond our control (humidity, temperature), which could affect our results. The wire will be the only variable- in the first test it will be the length; in the second it will be the thickness.

Prediction:

I think that the length of the wire will affect the resistance. I think that the resistance will be increased if the wire is longer. This is because the electricity will be slowed down for a longer time, so the current should drop.

The thickness of the wire will definitely affect resistance. The thicker the wire the lower the resistance will be. This is because the electrons will have more room to move and flow, and more can flow through the wire.

Conclusion:

My results show that both the length and thickness of a wire have an affect on its resistance. The graphs that I have made for the length of the wire shows clearly that the voltage increases, and the current drops when the wire is longer. This is because the electrons are being slowed down more and more, so the current will drop, and there is a higher voltage because the power being given out is not able to pass through the circuit quickly, so builds up. The other graphs also shows that the longer the wire is, clearly the resistance is higher. This is again, because the electrons are slowed down for a longer period of time, as they cannot pass through the wire as quickly as they could if it was short, so the resistance increases.

For width our results were a bit less accurate. The first graph that I made, showing the comparison between length and current, shows that the higher the voltage, the lower the current. Our results are slightly inaccurate because the graph actually contains a loop! Apart from those odd results, the graph shows pretty much what we predicted. This is because when there is less wires, the current cannot pass through it as quickly, as there is less room for all the electrons to pass through. Therefore the current drops, and the voltage increases, as there is a build of electrons waiting to pass through the wire. If the wire is thick, the electrons pass through it easily, so the current increases, and the voltage drops because there is not the build up of electrons that there was before. My seconf graph shows that the thicker the wire, the lower the resistance. Our results for one wire are very odd, as they are much higher than all our other results. Apart from that our results were much as we expected. Like I said above, this is because the electrons have more room to pass through a thick wire, rather than squeezing slowly through a thin one, so the thick wires had less resistance.

Evaluation:

There were a few problems with our experiment.

The temperature and humidity of the room may have varied slightly whilst conducting our experiments, especially seeing as we conducted them over two days. If it is hot, the wire will heat up and will affect its resistance.
For the experiment for the width of a wire, we used the same type of wire, but not the same wire itself. One wire may have been slightly thicker or thinner than another, but it would only have been marginal if there were any differences.
The wires contained slight bends and twists, which would have affected an accurate reading of the length, and possible (but unlikely) the resistance itself.
Obviously human error will have had some affect on our results. Even if I’m perfect, the rest of my group isn’t! The length of the wire may have millimeters out, the readings off of the voltmeter and the ammeter may have been slightly inaccurate, and possible even the calculations for working out the resistance.

I do not think that our results are void. I think this because the results we got were still fairly accurate (with the odd exception), and our predictions were correct. I feel they may have been more accurate if the experiment had been carried out over one day, as the temperature may have changed slightly, and the humidity. Apart from that I do not know how else we could have conducted that experiment better. The other problems that I stated above we could do nothing about, which is why I feel that our results are still valid.

Th☺mas Parr 1☺G1