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# Factors that affect the resistance of a wire.

Extracts from this document...

Introduction

James Pearson 11h

Factors that affect the resistance of a wire.

What I am trying to find out:

How the resistance of a wire will be affected when it is subjected to a varied number of factors:

• Temperature
• Cross section of a wire
• Material
• Length of wire

For this experiment I will be investigating how the length of the wire affects the resistance.

Prediction

I predict that the resistance of the wire will vary as the thickness, type and length of the wire changes.

For this experiment I predict that as the length of the wire decreases the resistance will become lower.

If the wire is twice as long it will have double the particles in it meaning there would be twice the resistance. If the wire is longer the more particles there are for the electrons to pass through making the resistance higher.

Wire A is 5cm long whereas wire B is 10cm.This means theoretically wire A should have half the resistance of wire B as there are half as many particles for the electrons to pass through.

Electrical resistance is a measure of a materials opposition to the flow of an electric charge. Resistance is usually given the symbol 'R'. The unit for electrical resistance is the ohm.

Ohm's law is the voltage drop (V) across a resistor proportional to the current running through it.

Middle

## Method

The wire will be held against the meter rule then cut 1 meter within the percentage error. The circuit will be set up as shown in the diagram above; The power pack will be connected to an ammeter, which is also connected to the experiment subject, the wire. Across this wire the voltmeter will be connected in parallel. Inside the power pack is the switch used to activate the current and the variable resistor to control the current so that the wire does not get too hot which will affect the resistance. A preliminary test will have to be carried out to determine a suitable current to keep constant that will not affect the heat of the wire too much.

The wire length will be measured to the nearest cm. Millimeters will be avoided because they would lead to using too many different lengths. The circuit will be put into action with 1m of wire in the circuit to begin with. The current will remain constant and the voltage recorded. The wire will then be reduced by 10cm every time then the experiment will be repeated using 90cm of the wire, then 80cm and so on until 10cm is left. The results will be recorded in a table.

#### Preliminary Method

A variable resistor will be used to change and control the current.

Conclusion

The increase in room temperature could prove to be a variable that largely affects the results. To combat this the temperature could be recorded alongside the experiment and could be used to construct a time > temperature graph. With this it would be visible on both graphs where the temperature and resistance fluctuates, if there are corresponding trends then it is possible to draw the conclusion that the room temperature does indeed affect the resistance.

The range of values could be made larger with smaller intervals. This would give a smoother curve on the graph, as there would be more points to plot. It would also be much more precise and make it easier to spot trends and patterns.

If I was to retake the experiment I would make a list of all the variables that can affect the resistance and make sure I am in an environment where I can control each one. I would use this as a preliminary experiment as now I have found out all the problems that can arise. Using the results and information gathered from this research I would go on to investigate the resistance of a wire further but not without prior knowledge of how to prevent other variables from affecting my results.

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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