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Wire length in relation to Resistance investigation

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Introduction

Wire length in relation to Resistance investigation PLANNING Task The aim of this investigation is to find out how the length of a piece of wire affects its resistance. Prediction I predict that as the length of the wire increases so will its resistance. This is because if the length of wire is doubled, the current (flow of electrons) will have to be pushed between twice as many atoms so the resistance should double as well. If we plot our results on a graph it should give a positive correlation if the resistance is directly proportional to length (as one increases so does the other). Method and fair testing The variable in the experiment that we are investigating is the length of wire. We will measure the voltage and current of the different lengths of wire at different voltages. We are going to test each length 4 times. We should get 4 slightly different resistance figures due to experimental error. For each length of wire, we will plot the current against the voltage and draw a straight line of best fit through these points. ...read more.

Middle

The experiment will be done in the classroom therefore the wire will neutrally be at room temperature. The equipment we will use is: a circuit board, an ammeter, a voltmeter, 100cm of wire, a power pack, 2 crocodile clips and wires. Diagram OBTAINING EVIDENCE Results Length (cm) Power pack voltage(V) Measured voltage (V) Current (A) 20 2 1.0 0.61 4 2.25 1.22 6 3.5 2.07 9 5.75 3.11 40 2 1.5 0.40 4 2.5 0.81 6 4.25 1.31 9 6.5 2.06 60 2 1.5 0.29 4 2.75 0.58 6 4.5 0.98 9 7 1.49 80 2 1.5 0.24 4 3 0.49 6 4.75 0.79 9 7 1.16 100 2 1.5 0.18 4 2.75 0.37 6 4.5 0.61 9 7.25 0.97 Length of wire Resistance (?? 20cm 1.76 40cm 3.31 60cm 4.80 80cm 6.13 100cm 7.65 ANALYSIS As you can see from our results table, we have found out that as we increased the length of wire, the resistance increased too. As the points lie in a straight line it also proves that the relationship is linear. ...read more.

Conclusion

Because the atoms would be further apart this might reduce the resistance slightly. To prevent this from affecting any other readings, we could put the wire in cold water after each reading, to cool it, or do the experiment with the wire in water. The problem with doing the experiment with the wire in water is that the current may be conducted through the water if it is not pure/distilled. This is because a trace of acid or alkali in the solution could conduct the current and prevent it going through the wire giving a false reading. To make our results more accurate we could take more readings by testing each length at other voltages (in addition to 2, 4, 6, and 9) and/or take readings of more lengths of wire. To make the experiment more accurate, we could first substitute something of known resistance so that the resistance of the remainder of the circuit can be accurately calculated. This can then be deducted from the results to obtain the exact value of the resistance of the wire. We could extend this enquiry by investigating whether the temperature of the wire affects its resistance and find the resistance of different metals. ...read more.

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