To find out how the resistance of a wire changes depending on its thickness.

The resistance of a wire can be affected by the following four factors;

        • Length of wire- The longer the wire the higher the resistance,

        • Temperature- Resistance can be affected by the temperature,

• Thickness of the wire (cross sectional area) - Less resistance for          wire of larger cross sectional area.

• Type of metal- Gold and silver have low resistances.

          The resistance of a wire can be calculated by using the following equation;

                

Resistance= Voltage

              Current

In our experiment we are going to investigate the difference in resistance of Various thickness wires.

    

Apparatus –   Batteries

• Voltmeter
• Ammeter
• Variable Resistor
• Five different thickness wires
• Connecting wires

Diagram-

Method-

1. Set up apparatus as shown on diagram.
2. Get five different thickness of wires.
3. Measure the thickness of each wire, three times to get an accurate average.
4. Attach the wire to a meter ruler, measure the length of the wire to 60 cm.
5. Connect one of these wires where specified on the diagram.
6. Take readings from both the voltmeter and ammeter and record the readings on a table.
7. Change the position of the resistor (Variable resistor) and take another set of readings.
8. For each different thickness wires change the position of the resistor 5 times and record the readings.

Prediction

         I predict the thinner the wire used in the experiment the more resistance there will be, due to the fact that the electrons will have a restricted amount of space, which will therefore increase the amount of times the electrons will have to bump into each other to flow along with the current, hence increase the resistance and also the current will be small. If the wire is thick, more electrons can flow more quicker, with the minimum amount of resistance. If the voltage is low, the current will be high because many more electrons can flow through a given point in a circuit.

Results

1-

2-

3-

Conclusion

        From our results we can clearly see that the thicker wire used in our investigation had the least resistant. This is because more electrons can flow without bumping into each other as much, therefore the resistance is low, the more electrons that pass through the wire at any given point increases the current as it is shown on our result table 2.

        E.g.

Cross section of a thick wire

More current flow

In this example we can see that more electrons can go through a wire at one time with less resistance. If we had a thin wire and made it double the thickness as it started off, the resistance is halved.

E.g.

Cross section of a thin wire

Less current flow

As we went through all the other SWG’s of wire (from thick to thin),

We found that the resistance increased when we got down to the thinner wires. This is due to the fact that that the electrons had to always bump into each other to move along the current, therefore the resistance is increased. The current is also low because only a minimum number of

electrons can go through a given point in a circuit therefore the voltage is increased.

Evaluation

        When we first carried out this investigation our results went horribly wrong. Firstly because we somehow managed to put the voltmeter in the wrong place, this gave us ridiculous results. Secondly, to give us reasonable results we had to have our wires the minimum of 50 centimetres, we made them 20 centimetres!

        The second time we carried out this experiment; we corrected our mistakes and got a better set of results. But I don’t think these result were that reliable due to the fact that that each wire did not have the same diameter all the way along the 60 centimetre length.

Kobir Ali