If the resistance increases due to the explanations above including the length of wire, temperature will increase. So it is very important to try to keep the temperature the same. Going onto to temperature, the temperature also affects the rate of resistance. If the temperature increases the resistance of a wire increases. This is because the atoms in the wire vibrate more when heated making it harder for the current to pass through the wire.
The last factor of resistivity is the change of the length of the wire. As the length of the wire doubles the rate of resistance will double. I think this is because the longer the wire, the more atoms there are for the current to try to pass. Therefore collision occurs affecting or increasing the rate of reactivity. Then of course if the length of wire is halved the rate of resistance is halved therefore proving my prediction and proving that the rate of reactivity is directly proportional to the length of wire.
Apparatus
Metre ruler
Crocodile clips
Wires
Power pack (D.C. supply)
Voltmeter
Ammeter
Constantan wire (diameter of 0.38 mm)
Diagram
Diagram set up as shown
Method
- First, the experiment is set up as shown.
- The constantan wire should be attached firmly and flatly onto the meter ruler. The length of the wire should be about 100 cm.
- The ammeter and the voltmeter should be placed correctly to show positive readings.
- Leads should be connected between the components in the circuit.
- Crocodile clips should be used to connect the constantan wire to the circuit.
- The D.C. voltage is then switched on to a previously determined voltage of three.
- Readings are then taken when the length of the constantan wire is at 10cm, 20cm, 30cm, 40cm, 50cm, 60cm, 70cm, 80cm, 90cm, and 100cm.
Using the results gathered from this experiment, the resistance of the specific length of wire can then be calculated. Resistance and be calculated using Ohm’s Law, which is shown below.
V= I x R or Voltage (Volts) = Current (Amps) x Resistance (Ohms)
Fair Test
Since there are four other types of factors that can affect the rate of resistance, these parameters in the experiment should be set up carefully so that it does not affect the rate of resistance. In this experiment the length of the wire will change from 0 to 100 and it should be made so that the length required for the results are accurately measured.
All other factors of resistivity must not be changed as they will affect the rate of resistance. I must make sure that the voltage and the current of the wire must not be changed either as this can affect the rate of resistance as well. Room temperature must remain constant as well.
Results Table
Analaysis
From the graph I have drawn, I can see that the resistance of the wire is directly proportional to the length of the wire, therefore proving my prediction correct. I know this because the line of best fit drawn is a straight line trough the origin showing that if the length of the wire doubles or halves then the resistance doubles or halves, in proportion to each other. Therefore this affects resistance.
The resistance of a wire depends on the number of atoms in the wire because the more atoms there are the more collisions occur with the electrons passing through the wire. Saying that the length of wire is directly proportional to the resistance, if the length increases in size meaning there are more atoms in the length of wire, the more collisions will occur.
In the graph, it has shown that the resistance (in Ohms) is directly proportional to the length of wire (in cm). This is shown when I moved the wire to a length of 10cm, the resistance changed to 1.18 and when the length of wire was moved to 70cm it moved to 7.18. If you were to draw a line between these two points you could be able to find the resistance of a wire at any length. This is because the resistance of a wire is directly proportional to length of wire. I think that my results are accurate enough to draw a good conclusion because the line of best fit is fairly accurate.
Evaluation
In the graph I have shown there is only one anomalous result, this could just mean that I have done a simple mistake while measuring the lengths required. Although I think this result is anomalous it is not far of the line of best fit. To improve my results a bit more to make it more reliable I could make more testing so that my average is better.
Even though the wire should be at the same diameter at all points, there still could be different diameters to some areas that could affect the results I had. Another factor that could have changed or did change my results is when I measured the wire and put in place as the wire was bent and I didn’t straighten it. Also the wire was not properly placed on the ruler as it was only celotaped on.
I could also have expanded my investigation further by testing the other parameters involved in this investigation. I could have tested different type of materials to find out what resistance went through them at a constant length. This would be done to see which material had the least resistance and the most resistance. I could have also tested the different diameters using the same metal to test how resistance is affected when using different lengths.
