# Investigate factors that affect resistance

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Introduction

Investigate factors that affect resistance

Introduction

During recent physics lessons, we have been studying resistance and what factors may affect resistance. So far, we have learnt that…

- Resistance is the opposition to the flow of electrical current
- It is caused by electrons colliding with the atoms in a metal
- The more collisions there are, the greater the resistance will be
- When electrons collide with atoms, the atoms absorb the kinetic energy from the electrons and vibrate faster
- This means the atoms and therefore the material is getting hotter
- The increased vibrations of the atoms make it harder for the electrons to get past and therefore the resistance is increased
- Resistance is the ratio of voltage divided by current
- Ohm’s Law states that for a metallic conductor the current through the wire is directly proportional to the voltage across its ends as long as the temperature remains constant

We are now going to investigate further into what factors affect resistance and how they affect it.

## Variables

The variables that I could use in my investigation are…

- Atomic structure of the metal (type of metal)
- Temperature
- Length of the wire

- Thickness of the wire

These are all factors that would affect resistance, but I am only going to investigate one factor.

## Chosen variable

The variable that I have chosen to use in this investigation is the length of the wire. I have chosen to use this variable as it would be the easiest to do as the length of wire is easy to measure and would probably give the most accurate results due to this. I have chosen not to change th type eof metal as this cannot be measured and would therefore be harder to analyse. It would also be more difficult to measure the thickness of the metal accurately with the equipment available. Changing the temperature of the wire would be hard to control making it harder to compare and analyse my results. Therefore, I have decided to use the length of the wire as my variable.

## Prediction

By using what I have already learnt about resistance, I predict that the longer the wire, the greater the resistance will be, for example, if the length of the wire if doubled, then the resistance will also double. This is because in a longer piece of wire, there will be more metal and therefore more metal atoms, and this means that there will be more collisions taking place between the metal atoms and the electrons in the current. This will therefore mean that the resistance will be greater as more collisions mean a greater resistance in the wire. When I plot my graph I expect to see a straight line through the origin which will show that the length of the wire is directly proportional to the resistance.

## List of apparatus

- Variable lab pack
- Connecting wires
- 1 metre ruler accurate to +/-1mm
- 0-15V Voltmeter accurate to +/-0.5V
- 0-5A Ammeter accurate to +/-0.2A
- 1 metre of swag 32 wire
- Micrometer accurate to 0.01mm

Middle

0.91

Length (cm)

Volts (V)

Current (A)

Resistance (Ohms)

10.0

1.5

3.2

0.47

20.0

2.0

2.2

0.91

30.0

2.2

1.6

1.38

40.0

2.4

1.3

1.85

## Method

## Collect the apparatus and set up as shown in the circuit diagram. Using the micrometer measure the diameter of the wire, record the result three times and work out the average. Place the wire clip 10cm along the wire and record the current and voltage in a table of results. Repeat this at 10cm intervals until you reach 1 metre. Repeat this three times recording your results each time. When you have recorded all the data, work out the average resistance by dividing the voltage by the current. Plot your results on a graph and draw a line of best fit.

## Chosen measurements

Swag: 28 Number of readings: 10

Voltage: 4V Ammeter range: 0-5 A accurate to +/-0.2A

Conclusion

### Evaluation

The results of my experiment were relatively accurate as we measured the current on an ammeter which was accurate to +/- 0.2 Amps and a voltmeter that was accurate to +/- 0.5 Volts. To make our readings more reliable, we took repeated the experiment three times and worked out the average current, voltage and resistance. There was very little variation in out readings so this means that the results would be reasonably accurate. To improve the experiment, we could use more accurate meters, for example digital meters which are accurate to +/- 0.001 Amps and +/- 0.001 Volts. This would mean that the results would be more accurate and therefore more reliable. Additionally, I could take readings at smaller intervals so that I could put more points on the graph of results. This would mean that my results were more reliable and I could be sure that my findings were correct. To extend this investigation, I could investigate other actors that affect resistance, for example the thickness of the wire, the temperature of the wire and the type of metal.

Alicia Corby 10T1/10U1

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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