The power supply will beat the same setting all the way through the experiments will the same material same piece of wire.
The factor that I am going to investigate is the length of the wire. I will constantly increase the length by 10cm starting at 10cm and ending at 100cm. Current is the flow of electrons around a circuit. For an electric current to flow, there must be no gaps in the circuit. Electrons flow from atom to atom round from the negative pole to.
A Fair Test:
It would be a very good fair test if I could keep the temperature of the room the same, but it wouldn’t be possible, as it is hard to predict the temperature and keep it the same. I will only change the variable, which in this case is the length of wire. I will do each test three times; this will give me a balanced result.
Predication:
I predict that what will happen is the longer the wire the more resistance there will be. I think this because there are more atoms which will disturb the electrons as they pass through the wire. This is because in a longer wire, there are more wire particles that electrons can bump into. Resistance is caused by electrons colliding with wire particles. If there are more wire particles, the chance of an electron colliding with a wire particle will be higher.
I will have to keep the voltage low to minimize resistance. This is due to kinetic theory, the more voltage, and the hotter the wire, the faster moving particles therefore the more energy lost through collisions.
Preliminary test:
To see what voltage I should use, I tested the wire using different potential difference from the power pack, when the wire glowed red hot, it meant that I couldn’t use a higher voltage, as it would have been a safety hazard, and may have caused a fire. I also checked the thickness through out the wire.
Apparatus:
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The apparatus which I will have to use are:
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Crocodile clips
You’re Experiment:
Before I start the experiment the teacher will check it. I will pass a current through a piece of wire, the wire carries a resistance, and this causes the electrons to hit the atoms. I can test how the resistance changes in the different wire lengths; I will increase the voltage to ensure that the current is kept the same. I will not change anything apart from the length of the wire from 10cm to 100cm. I made a record of the current and potential difference, via the voltmeter and the ammeter. My results are reliable as I did the experiment three times. Every time the readings were similar proving that there was no mistake in collecting the results.
My results could have been more exact if more accurate instruments were used. Unnecessary loss of heat within the connecting leads may have been a factor affecting accuracy.
Diagram:
Safety:
- Make sure hands are dry.
- Be careful when handling wires they might get hot.
- Do not let the wire get to hot or it will burn.
- In order to perform a safe experiment, a low voltage of 2V was chosen so that overheating was minimilised.
- Before switching on the power ensures that the circuit is complete.
- Students work in small groups, so that every thing is under control.
Analysis:
When I increased the wire length the resistance also increased.
Table of Results
Evaluation:
The results that I got were very good, they were all accurate. I took 3 readings and used the average. 3 out of 10 points did not fit the line; this may have been prevented if better instruments were used, when attaching the crocodile clips to the wire this could have been carried out with more care.
My method was suitable as I got the results I wanted, the experiment could be repeated on a larger scale to make less room for error think that better equipment would have given more precise results.
To improve the experiment, the clips could be attached more carefully; a more accurate ammeter would make sure that the current is always exactly the same. A better voltmeter would have given better resistance results. The wires and clips used would also have an effect on the resistance; the wires could be insulated better to reduce heat loss. The results would then contain no anomalies. The above would definitely produce better events.
- You could compare resistance to a high street. If you walk down one street and bump into a certain amount of people, in a street twice the length you are likely to bump into twice that certain amount of people. It is in this way that resistance works.
During this experiment I have found out many things such as:
- The resistance of a wire depends on its thickness
- The thinner the wire, the higher it’s resistance
- You must use thick wire to carry a large current or the wire will get too hot and melt.
