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# Electrician asked to repair an old radio. He believes that he needs a resistance of 1.9 ohms, which is not easily obtained - investigation to help him resolve the problem

Extracts from this document...

Introduction

Physics coursework

An electrician has been asked to repair an old radio. He believes that he needs a resistance of 1.9 ohms, which is not easily obtained.

I have been provided with some reels of resistance wire and I will plan and carry out an investigation to help the electrician solve his problem.

I believe there are a certain number of independent variables which may influence the resistance of a wire; 1) The temperature of the wire

2) The diameter of the wire

3) The length of the wire

4) The type of wire

I am choosing to investigate the length of the wire because I believe it affects resistance, as my scientific knowledge tells me;

Current

For current to flow, there must be a complete circuit. Current flows from the positive to the negative terminal of the power supply, but electrons flow in the opposite direction. Current is measured in amps (A) by an ammeter connected in series with a component in the circuit. The current is driven round a circuit by voltage of the power supply or potential difference.

Current= potential difference

Resistance

## Voltage

Potential difference is measured in volts (V) using a voltmeter connected in parallel across a component in a circuit.

...read more.

Middle

Average reading (I)

Average Resistance(ohms)

0.50

0.16

0.16

0.16

0.16

3.125

0.75

0.24

0.24

0.24

0.24

3.125

1.00

0.32

0.32

0.32

0.32

3.125

1.25

0.42

0.42

0.42

0.42

2.980

1.50

0.50

0.50

0.50

0.50

3.000

80cm:

 Voltage(V) Reading 1(I) Reading2(I) Reading 3 (I) Average reading (I) Average Resistance(ohms) 0.50 0.20 0.20 0.20 0.20 2.5 0.75 0.30 0.30 0.30 0.30 2.5 1.00 0.41 0.41 0.41 0.41 2.44 1.25 0.51 0.51 0.51 0,51 2.45 1.50 0.61 0.61 0.61 0.61 2.46

60cm:

 Voltage(V) Reading 1(I) Reading2(I) Reading 3 (I) Average reading (I) Average Resistance(ohms) 0.50 0.28 0.28 0.28 0.28 1.79 0.75 0.42 0.42 0.42 0.42 1.79 1.00 0.57 0.57 0.57 0.57 1.75 1.25 0.72 0.72 0.72 0.72 1.74 1.50 0.86 0.86 0.86 0.86 1.74

40cm:

 Voltage(V) Reading 1(I)
...read more.

Conclusion

We could extend the experiment by perhaps using much smaller and/or much bigger lengths of wire to see if the mathematical procedure works exactly the same. This experiment would be carried out in exactly the same way as the one above but using different values for the length of wire. This would create a greater range of results, therefore making the whole experiment more reliable. To improve the reliability we could use a larger rheostat, making it easier to get the exact voltage and therefore creating more accurate results. Using a wider range of voltages to further test the findings could also extend the experiment.

...read more.

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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