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# Resistance of a wire

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Introduction

Title: Resistance of a wire Aim: To see how the length of a wire affects its resistance Apparatus: Power Supply (Batteries) Connecting wires Meter stick Constantan wire Ammeter Voltmeter Crocodile clips Prediction: I predict that the length of the wire will be proportional to its resistance, for example if the length were to be tripled the resistance would triple. Background information: An electrical current is the flow of electrons in a conductor. When electrons collide with one another they pass on some of their energy, this causes the increase in the temperature as the atoms begin to vibrate. As the temperature begins to increase it becomes more difficult for the electrons to pass through, as the resistance increases there is less current. Ohms law is used to find the resistance it is measured in ohms, the formula that is used is voltage divided by current. Method: o Set up the apparatus as shown in the diagram above. o Measure the wire to 10cm. o Connect crocodile clips to either end of the taut wire and insert into the circuit. o Close switch to complete the circuit. ...read more.

Middle

Results: Length (cm) Voltage (V) Current (A) Resistance (Ohms) 10 0.43 3.05 0.14 20 0.66 2.46 0.27 30 0.80 2.07 0.38 40 0.93 1.77 0.53 50 1.02 1.55 0.66 60 1.08 1.39 0.77 70 1.16 1.28 0.91 80 1.20 1.67 1.21 90 1.24 1.06 1.17 100 1.30 1.02 1.27 Length (cm) Voltage (V) Current (A) Resistance (Ohms) 10 0.42 3.04 0.14 20 0.66 2.44 0.27 30 0.80 2.09 0.38 40 0.94 1.77 0.53 50 1.03 1.56 0.66 60 1.10 1.42 0.77 70 1.18 1.30 0.91 80 1.22 1.18 1.23 90 1.25 1.07 1.17 100 1.31 1.01 1.29 Analysing results: After reviewing my results, which are displayed in both of my graphs, I notice that the length of the wire is proportional to its resistance. As we can see from both of my graphs, they show positive correlation with only two identical anomalous results. I can tell that from these results there must have been faults in the wire as the same set of results appear in each graph. ...read more.

Conclusion

There could have been a manufacturing fault this would have caused the cross sectional area to be low. Other reason for the resistance of the wire to be to low at 90cm could be due to the fact that there were kinks in the wire causing the wire to increase in length. I personally think that there was a fault in the wire as the anomalous results were identical in both sets of results. I could have changed my method in a numerous amount of ways in order to make my results more accurate. I could have switched off the power for longer periods making sure that the intervals were equal, and that the wires had an efficient amount of time to cool. A piece of string could have been used instead of the meter stick, as it is able to bend to the shape of the wire unlike a ruler. I could have extended my investigation by using different types of wires, for example different thickness and diameter could have been used. Also a different voltage and current could have been used to prove my original prediction that length effects resistance. ...read more.

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