# Factors affecting Resistance.

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Introduction

Factors affecting Resistance

Plan:

The Task of this investigation is to find out the factors that affect the resistance of a wire.

This will be done by performing experiments that try and investigate different proposed factors and to see whether they affect the resistance.

Resistance is the force, which opposes the flow of an electric current around a circuit so that energy is required to push the charged particles around the circuit. Resistance is measured in ohms. A resistor has the resistance of one ohm if a voltage of one volt is requires to push the current of one amp through it.

Resistance occurs when the electrons travelling along the wire collide with the atoms of the wire.

These collisions slow down the flow of electrons causing resistance. Resistance is a measure of how hard it is to move the electrons through the wire.

Wire length: If the length of the wire is increased then the resistance will also increase as the electrons will have a longer distance to travel and so more collisions will occur. Due to this, the length increase should be directly proportional to the resistance increase.

This tells me that the voltage measures the amount of energy used up in getting each coulomb of charge through the wire. The units of volts are the same as joules per coulomb. Therefore, Ohms law says the more resistance means more energy used to pass through the wire. Resistance is a measure of how much energy is needed to push the current through something.

Middle

10

0.7

0.2

2.9

15

0.7

0.2

3.5

20

0.8

0.15

5.3

25

0.85

0.1

8.5

30

0.875

0.1

8.75

35

0.9

0.1

9

40

0.9

0.1

9

45

0.9

0.1

9

50

0.9

0.1

9

55

0.9

0.1

9

60

0.9

0.1

9

65

0.9

0.07

12

70

0.9

0.075

12

75

0.9

0.07

12

80

0.9

0.075

12

85

0.9

0.07

12

90

0.9

0.075

12

95

0.9

0.07

12

100

## Observation

The results from my experiment, does have a relationship with the length of the wire, but its not necessarily in direct proportion to the length of the wire.

For example: Between 5-40cm of wire, the resistance is about what I expected, it is always increasing because the longer the wire the more atoms and so the more likely the electrons are going to collide with the atoms.

Between 40-65cm of wire, the resistance stays at a constant 9 ohms. And between 70-100cm of wire it has a resistance of 12 ohms. This could be because only 12v was travelling through the wire and therefore wasn’t powerful enough to change the resistance after a certain point. One thing, which is unknown, is the resistance goes up to 9 ohms and suddenly jumps to 12 ohms. This could be because of inaccurate results as the experiment was only taken once.

Analysis:

Through my experiment and observations. I have found out that the resistance isn’t to direct proportion to the length of the wire, because this would mean, 30cm of wire = resistance of 8.5 ohms. So 60cm of wire would = resistance of 17ohms.

Conclusion

Apparatus for future experiments:

- Digital Voltmeter, and Ammeter. This would give very accurate results
- Selection of wire, thicker wire with a higher voltage going into the wire, may give an more accurate result.
- Higher voltage power pack, on my graph I found that my prediction seemed to be correct at the beginning, but went out of the proportion later on. I think this could have something to do with the voltage, as it’s responsible for the resistance in the first place. A power pack, which goes up to 30 volts, would be good.

Supporting my conclusion:

I have said this under the Analysis, but here it is again. I think that my results could be suitable to confirm my prediction and support a conclusion. However, the results I would have to double-check, as it doesn’t match my prediction. I know that my prediction is correct because outside resources (Textbooks and Britannica) say that ‘the length increases in direct proportion to the resistance. ´

The experiment is repeatable, by using the method, but factors like temperature, length of wire, Diameter or thickness, and the type of metal affect the resistance so these factors have to remain constant throughout the next experiment.

By Alex Barber 10RA

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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