Apparatus:
- Ammeter
- Voltmeter
- Power Pack
- Roll of Nichrome Wire
- Meter Ruler
- Crocodile Clips
- Wire Cutter/Scissors
- Sticky Tape
Method:
- Gather all the necessary equipment.
- Take the Nichrome Wire only and the meter ruler. Tape one end of the Nichrome Wire on the zero end of the ruler.
- Measure and cut using the scissors/wire cutter wires with the size of 10 cm; 15 cm; 20 cm; 25cm; 30 cm; 35 cm; 40 cm; 45cm and 50 cm.
- Then assemble the circuit as shown below and in place of the resistor use the 10 cm Nichrome Wire. Keep the crocodile clips attached right at the end of both sides of the nichrome wire in order to get the resistance of the whole wire.
- Turn on the power pack. Keep the EMF/Voltage at 3 all throughout the experiment and record the readings from the ammeter and the voltmeter and note these down.
- Then repeat the above steps 4 and 5, with the other remaining eight different lengths of wire in place of the 10 cm wire.
- Note down all the results in a suitable table format.
- Then calculate the resistance for each length of wire, but using the formula, “Resistance = Voltage/Current.”
Data Collection:
Results:
Data Analysis:
Analysis of Results:
Conclusion:
As can be seen from the graph and the results it is easy to conclude that my hypothesis that the longer the wire the higher the resistance was correct. The Length of the nichrome wire and the resistance are both directly proportional to each other. As the length increases the resistance will also increase. This can be seen clearly from the graph above. Firstly the graph has a steady straight best-fit line, secondly the best-fit line is going through the origin and thirdly all the points are near the best-fit line. Thus this clearly shows that when one is doubled the other also doubles. There are several examples of this in my results table. For example if we take 10 cm and 20 cm example. The resistance at 10cm is 0.433 and at 20cm the resistance is 0.895. If we are doubling the length from 10 to 20 the resistance can be seen doubled also. There might be some difference when doubled as due to errors, but overall the wire resistance and length of the wire are directly proportional because as one doubles the other doubles too.
Hence there is strong positive correlation between the two factors, and thus when the length of the wire increases the resistance also increases. The reason for this result has already been mentioned before in my hypothesis. The longer the wire the higher the resistance because as the length of the wire increases there are more wire particles. Electrons colliding with the wire particles cause resistance. When there is a longer wire there are more wire particles and therefore there are more particles for the electrons to collide with, leading to a higher resistance.
In a longer wire, it is obvious that the electrons would have to collide with a larger number of wire particles. To understand this better we can compare resistance to a corridor. If we imagine we are the electrons moving through a corridor of size 25 meters, filled with 10 people. If we doubled the size of the corridor to 50 meters, the amount of people would also increase to 20. Therefore if we have to run through the corridor we have to avoid a larger number of people, and have a higher chance of banging into more people compared to the shorter corridor. In a summary I would say that I have accomplished my aim and also found that my hypothesis was correct. Hence the relationship between the lengths of the wire and the resistance is directly proportional and if one doubles the other doubles too.
Evaluation:
From my results table and the graph I can see that my results that I have collected are very reliable. This is because all the points on the graph are on or near the best-fit line. But there are some errors which could have occurred in the experiment, which are as written below:
- Length of Wire not accurate as it could have missed off by some a few centimeters affecting the whole experiment.
- Readings taken off Voltmeter and Ammeter could have been incorrect. This could have caused the resistance to be wrong, either higher or lower.
- The crocodile clips put on, might have not been put at the end, causing the results to be incorrect, as the resistance would not have been found of the whole wire.
- Connections could have been faulty causing difference in resistance.
- Difference in other variables. For example temperature could have changed. For a small length, the voltage of 3 is high causing the wire to heat up and increasing the resistance of the wire.
- Using old apparatus, could have given wrong results too.
Improving the errors above can be done as written below:
- (for error 1) Have the wire really tight, in order to get the length correct, and let two to three people help in measure, as two people can hold at the two ends, and one cutting the wire.
- (for error 4) Ask the teacher to check the circuit, and after changing each length, check whether the circuit is in place correctly.
- (for error 5) Keep the voltage lower, and rather than keeping the power pack on for a long time, quickly turn it on, and take the readings off the ammeter and voltmeter. (for error 6) Ask the teacher if the school as electrical ammeter and voltmeter. This would give better and accurate results.
Errors 2 cannot be improved upon as taking accurate readings off non-electrical ammeters and voltmeters is not possible. Error 3 cannot be improved upon also because crocodile clips keep moving and thus keeping an eye on them always is not possible. The improvements written above are suggestions only, but not 100% guarantee that after improving on the errors, the results will be 100% accurate. Not all errors can be fixed upon 100% as there is always a chance that human error will occur.
The experiment can be extended in the possible ways:
- Looking at other variables as written below
- Length of the Wire
- Thickness/Width of the Wire
- Material of the Wire
- Temperature
- EMF Supply
- Wire Density
- Perform the experiment with each wire several times. Then averaging the results out would give more accurate results.
- Getting results for different wire lengths like 100 cm.
