Bigger area has more current because there is more space for the electrons to pass through. The current would be high and the resistance would be low.
HOW RESISTANCE MIGHT BE AFFETED BY TYPE OF METAL
Length, area and temperature are kept the same. Different types of metals have different number of obstructions or resistivity. In a given volume it has its own number of nuclei and electrons.Ife we have a higher resistance, the higher the resistance and low current.
Trial experiment was done because we wanted to know which metal and area (swg) was appropriate for the final experiment. I chose nichrome and 26swg because it gave the biggest range of readings and the wire did not burn either. I didn’t choose copper and constatine because the readings were too small. I chose 26swg because it gave the biggest range of results and the wire didn’t burn. When the area is too small the current would be less too. When the area is big the current would be more as well.
APPARTUS
- Power Pack
- Ammeter
- Voltmeter
- Circuit wire
- Metal wire
- Crocodile clips
- Circuit leads
- Ruler
- Wire cutter
- Safety goggles
METHOD
- Set up the circuit as shown:
- Then cut up the length of wire needed and place it on the ruler using crocodile clips.
- Switch the power pack on to a voltage of 6 and collect the results.
SAFETY
- Don’t touch the wire while its still hot
- Don’t touch the equipment while it’s still hot or you might burn yourself.
- Make sure the voltage on the power pack is on a 6 and not higher or the wire will burn.
- Equipment must be kept away from sources of heat
eg. Radiators
FAIR TEST
- Reset the ammeter and voltmeter after each reading to make it fair and the results more accurate.
- Make sure the voltage on the power pack, the temperature, thickness of the wire and the metals are the same.
OBSERVING
Metal chosen: Nichrome
SWG chosen: 26
Resistance calculated by the formula:
1ST READING
2ND READING
AVERAGES
ANALYSIS
In the graph, the points are in a straight line .Therefore the pattern is that the resistance is proportional to length. As the graph shows, double the length and the resistance also doubles.
The above results prove that as we double the length, the resistance doubles. This is because the current in a short wire would be high due to fewer obstructions (positive nuclei).This allows the electrons to pass through providing a large current and low resistance. The other reason is that it has a shorter distance to travel. Whereas, the resistance in a long wire would be large and the current would be less because a longer wire has more obstructions and so fewer electrons can get through. The other reason is that it has a longer distance to travel.
We use the equation to see if the equation was correct. The equation proves to be wrong because the prediction results do not agree to the average results we got which can be referred by looking at the graph. The results from the prediction varies a lot from the results we got.So, the graphs does not agree with the prediction.
EVALUATION
To get better accuracy and reliability, I did the experiment twice and took an average. To make my results more accurate I used 2 decimal places as well. In the graph one of the point did not fall in with the straight line. The predicted graph was not the same as the graph we got in the practical. It could have been due to manufacture problems, crooked wire that could change the length or the use of crocodile clips.
The average readings varied a lot from the predicted results:
The average readings doubled from the predicted results. The readings are higher than what it should have been. This could have been because the voltmeter and ammeter was flickering all the time or the length of the wire might have been measured wrong. It might have also been that the wire was getting hot and the readings got higher. Crooked wire and the thickness of the crocodile clips would also change the results introducing an error. During the experiment I made a mistake and put the voltage on the power pack at 3 which was too low when it should have been at 6.This made my results unreliable and the readings were negative. To improve it I did the experiment once again. Next time, I would make sure the wire is more straight and to use pins instead of crocodile clips to confirm my prediction and prove my hypothesis.
