I predict that the bigger the area of the wire, the lower the resistance. Also, I predict that the effect of changing the wire length will be that as the length increases, the resistance on the wire will increase. This is because a long wire will contain more atoms ‘bumping’ around hitting each other therefore you would expect the resistance to increase.
In the long wire, there are more atoms therefore more collisions will take place. Therefore I am going to look at my prediction that as you double the length, you double the resistance.
The Apparatus I will use are as follows:
- 6 Volt battery
- Variable Resistor
- Ammeter
- Voltmeter
- 0 – 100cm of Constantan, Nichrome and Manganin wire
The below diagram shows the circuit I will set up:
Results
The below tables show my results from the investigation. I used three different wires: Manganin, Nichrome and Constantan. I have noted down the Voltage, current and resistance and have checked my results an extra time to find an average. Before I started taking the results I decided to take a preliminary result. This was:
- Variable resistor was low = 1.4 Volts
= 0.25 Amps
- Variable resistor was high = 4.8 Volts
= 1.25 Amps
- Variable resistor in the middle = 2.4 Volts
= 3.5 Amps
This tells me that keeping the variable resistor in the middle will be best because the voltage is not to low or not too high. Also, the wire will get to hot if the variable resistor is high and may affect my results. When the resistance is to low, there won’t be a big enough distance.
Results
This graph shows the Voltage, Current and resistance of the wire. This shows that as the length increases, so does the resistance.
Conclusion
From the table, you can see that as the length of the wire increases, the resistance also increases. Due to some results which didn’t fit in, I had to draw a line of best fit. In my hypothesis, I predicted that the effect of changing the wire length will be that as the length increases, the resistance on the wire will increase. This, following my results, is true. I did though take the results twice and then find an average between the two. This ensured accuracy encase there was one false result.
Evaluation
On the whole, I think that this investigation went quite well and I believe I carried it out to the best of my ability in the conditions provided. I tried to ensure that the wire in the circuit didn’t get to hot. I also tried to ensure also that the variable resistor stayed in the middle throughout the investigation. My range of results was adequate to plot a graph which supports my hypothesis, giving enough evidence to support a firm conclusion. There is not a great difference between my first and second set of results, showing that they are reasonably accurate and reliable. The ‘line of best fit’ fit well with my results which were fairly consistent, showing that the tests were carried out fairly accurately.
I chose this method of setting up my circuit because it is standard and also it is the simplest and easiest to set up. I set up my circuit so it would be easier when changing the wire. In this way, I can use the same circuit for each wire. This also ensures accuracy.
To extend this investigation, I would investigate my other prediction:
The bigger the area of the wire (thickness), the lower the resistance.
In doing this, I could keep the same circuit as I already have but change the area (thickness) of the three wires. I would use the same length for each wire and I would record the results from three different thicknesses for each of the three wires. These would be at 24, 26, 28 and 30.
