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Factors that affect the resistance of a wire.

Extracts from this document...

Introduction

GCSE Physics Practical on Resistance

The factors that affect the resistance of a wire include: -

1. The temperature that is applied to the wire – control variable
2. The length of a wire – independent variable
3. The thickness of the wire – independent variable
4. The type of wire used – control variable

The factor that I am choosing to vary is the length of the wire.

Prediction

I predict that as the length of the wire increases, the resistance of the wire will increase at a directly proportional rate.  If the length of the wire decreases, the resistance of the wire will decrease at an inversely proportional rate.

Background Research

If the length of wire is doubled, the resistance should also double. This is because if the length is doubled the number of atoms will also double resulting in twice the number of collisions, which speeds up the electrons and increases the resistance.  The voltage flowing through the circuit will be varied.  Ohm’s Law states that the current flowing through a metal wire is directly proportional to the potential difference across it.  Resistance = Voltage        R = V

Current               I

Preliminary Experiment

I did a preliminary experiment before I did the proper experiment to give myself an idea of what I needed to do and what measurements that I was going to be using in the proper experiment.  Keep the voltage in the circuit constant at 2 Volts.

Middle

A pen – to mark the 10 cm intervals on the wooden stickTwo crocodile clips – to clip at each end of the wire

Method

1. Make a circuit as shown below.  Connect the voltmeter in the circuit shown below together in parallel.
1. Set the voltage to 2 Volts on the Power Pack to begin with. This will be the controlled variable and the length will be the independent variable as it will be changed and measured before calculating the voltage and current flowing through the wire.
1. The voltage and current will be used to calculate the resistance of the wire.  The length of the wire would start off at 10 cm and will be increased by 10 cm until it reaches 100 cm.
1. The voltage and current should then be recorded for each length of wire.  The current and voltage will be recorded three times for each length of wire between 10 cm and 100 cm as the length is increased by 10 cm each time.

Conclusion

I have concluded an experiment that used a lot of results.  This helped to see a clear graph and notice if there were any anomalous results.  If there were anomalous results, they would be easy to spot because three measurements were recorded for each of the ten lengths between 10 cm and 100 cm.  My measurements were very reliable because the circuit was connected properly and was secure.  The equipment that I used was good and did not give me any problems.

The crocodile clips could have also been connected more securely to the wire so that there is a good connection for the circuit.

Sources

My own knowledge

Research from the Encyclopaedia of Britannica

Formulas and explanations from the GCSE Longman Study Guide – Physics

Mrs Roberts – Physics Teacher

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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