The shorter the wire, the less the resistance. This is because the electrons have a shorter distance to travel, so they will not use as much energy.
Prediction:
I predict that the longest wire will have the greatest resistance. As the length of wire increases, so does the resistance. I think this because, the more the electrons flow, the more they heat up and move quicker causing them to collide with other electrons, increasing the resistance.
Plan:
Variables:
In my experiment, I am going to vary the length of the wire because I want to investigate whether the length of the wire will affect the resistance flowing through. I will take the readings at every 5cm’s to compare the resistance between each length. I will calculate the resistance by dividing the voltage and current.
To keep the test fair:
I will keep the same wire;
If I changed the thickness of the wire in between the taking of readings, the resistance will vary. This is because a thin wire does not have much space for electrons to flow so they will collide with one another creating more resistance. If the wire is thicker the electrons have more space.
I will use nichrome wire. I will not change the material of the wire because different materials have different resistances and some conduct electricity better than others.
I will measure the wire accurately will a ruler to make sure I have the right length of wire.
I will use the same power supply so there is not a higher current going through the wire.
The experiment will be repeated 3 times for accuracy and thereafter an average will be calculated.
Equipment:
- Nichrome wire SWG 24
- Power supply
- Connecting wires
- Voltmeter
- Ammeter
- Crocodile clips
- Ruler
- Resistance board
- Variable resistor
Diagram:
Safety:
I will not touch the wire until it has cooled down
I will put the stools under the desk
I will carry equipment safely
I will always keep an eye on the experiment to make sure the wire does not burn
I will not touch the power supply with wet hands
Method:
- Collect all equipment required
- Set the equipment as shown in the diagram
- connect crocodile clips which are connected to the circuit to the resistance board at 5cm so only 5cm’s of the wire is connected
- switch on the power supply and take down the reading from the ammeter and the voltmeter
- do this another 2 times
- repeat this at 10cm, 15cm, 20cm, 25cm, 30cm, 35cm and 40cm, 3 readings on each length switching the power supply off at every reading
- write down your current and voltage variables in a table and then average your 3 readings on each length
- calculate the resistance on each variable
- finally draw a graph showing your results and analyze them
Preliminary test results:
The preliminary test shows:
As the length or the wire increases, the current decreases.
As the length of wire increases, the voltage increases but after 25cm, the voltage stays at 2v.
As the length of wire increases, the resistance increases.
The preliminary test shows what I had predicted.
In my main test I will take the reading of each length 3 times which will give me more accurate results.
I will need a better wire because the wire we used was not accurate because it was not straight.
The main experiment:
My results were as expected, as the length of wire increased, so did the resistance. This shows there is more resistance in a longer wire than a shorter wire.
Conclusion:
The conclusion I have reached is, the longer the wire, the higher the resistance. I know this because in my experiment, as I increased the length of the wire and worked out the resistance, it showed that the resistance increased too.
I think the results were as expected because the electrons in the longer wire had further to travel than the shorter wire, as a result the electrons in the longer wire used more energy. As the electrons travel very fast, they collide and lose energy resulting in a high resistance.
In the shorter wire, there was not as much wire to travel through so the electrons do not collide as much; therefore they do not use as much energy, meaning less resistance.
This experiment proved that my prediction was correct. As the length of wire increased the resistance increased too.
Evaluation:
Overall I think my experiment went as planned. My results were reliable because I made the experiment fair by measuring the wire accurately with a ruler and switching the power supply off each time I took the readings.
I have enough results to reach a conclusion because there is a pattern in my results. It shows how the length affects the resistance in the wire.
I had 1 reading which did not follow the pattern on the graph. I think this happened because we needed to let the wire cool down, the rest of my results were very accurate and reliable.
If I did this experiment again, I would use a new resistance board so the wire will be straight and the results would be more accurate. I would also use a more accurate voltmeter and ammeter, and I will wait a bit longer for the reading.
By doing this experiment, I found out how current, voltage and resistance are related. I also found that the longer the wire, the more the resistance and the shorter the wire, the less the resistance.