i.e. I= I 1 + I 2 + I 3
Aim:
To see how the length of a wire affects the resistance of electricity in a series circuit.
Safety:
- If hands are wet, dry them before using electrical equipment.
- Do not put the voltage to high.
- Be careful with all equipment.
- Do not touch wires which are either split or have no plastic casing when they are connected to a power supply.
Fair Test:
Temperature must be constant.
You can’t do half the experiment one day then do the rest the next day because the temperature may have changed dramatically. Cut the wires precisely to the size you need them to be.
Apparatus:
Ammeter Voltmeter Wire and Clips
A.C Power Pack Variable Resistor
Circuit Diagram:
Method:
- I will set up the circuit as shown above.
- I will connect in a series circuit with an A.C. power supply, setting the value to an appropriate voltage.
- I will then connect a wire which has a thickness of 26cm to the output from the ammeter.
- I will then connect the voltmeter across the wire I am testing.
- I will then connect the negative terminal of the voltmeter to the negative terminal of the power supply, therefore completing the circuit.
- I will repeat the above process for all the required thicknesses of wires that are going to be experimented.
- Because the thinner wires become quite hot, the readings must be taken quickly, but I will allow the wire to cool down before the next reading.
- I will repeat the whole experiment again, this time starting off at the thickest wire and going down to the thinnest.
- I will then record the resistance for each thickness of wire after the wire had been disconnected from the circuit.
Prediction:
I think as you increase the thickness of the wire, you also increase the amount of resistance. The current is the flow of electrons; the current is dependent on the amount of voltage, which is applied. Voltage is the push given to the current. The current has to go through a circuit, which contains resistance so if you increase that push you also increase the flow of the current. All materials have a slight resistance to electricity factors affecting the resistance are: Length, Voltage & Temperature and Surface Area.
Length:
The longer the wire the more the resistance because electrons will be colliding more frequently and energy will be lost as a result.
Temperature and Voltage:
Temperature has an affect on the experiment as the voltage has control over the temperature. The more the temperature, the more the particles vibrate, leading to a reduction in output voltage although not by a huge amount.
Surface Area:
Surface area has a large affect on the amount of resistance. The resistance depends upon the amount of denseness e.g. a large surface area has less resistance because a small area has tightly packed atoms which will make more collisions.
Results:
Here are the results I obtained during this investigation.
Below is the graph for the results above.
Conclusion:
Above is the graph for how the thickness of the wire affects the resistance. As you can see from the line of best fit, there is a positive correlation. This shows that as the thickness of the wire increases the resistance also increases. My prediction was correct as I said this would happen.
The thickness of the wire affects the resistance of the wire because the number of atoms in the wire increases or decreases as the thickness of the wire increases or decreases in proportion.
The resistance of a wire depends on the number of collisions the electrons have with the atoms of the material, so if there is a larger number of atoms there will be a larger number of collisions which will increase the resistance of the wire. If a certain thickness of wire contains a certain number of atoms when that thickness is increased the number of atoms will also increase.
Evaluation:
I enjoyed carrying out this investigation. I didn’t come across any problems while trying to set up the circuit. Everything was done correct and I got no anomalous results when I took the readings. These results aren’t very accurate because I only took one reading for each length of wire. If I had taken two or three readings for each length, then I could have found the average. This would have been more accurate. If I did this experiment again then I would use a resistor rather than a variable resistor because the results are unreliable. They are unreliable because everyone would have different results due to how they set up the resistance on the variable resistor.
