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# Resistance of a wire

Extracts from this document...

Introduction

## Resistance of a wire

Background Information

What is resistance?

Resistance is anything that causes an opposition to the flow of electricity in a circuit. Everything in the circuit causes a resistance! The higher the resistance in a wire, the more collisions there are inside the wire and the harder it is to push the electrons around the circuit.

Ohm’s Law

R = V/I

A steady increase in voltage, in a circuit with constant resistance, produces a constant linear rise in current.

A steady increase in resistance, in a circuit with constant voltage, produces a progressively weaker current.

Current is directly proportional to voltage and inversely proportional to resistance. This means that the higher the voltage, the higher the current, assuming resistance is kept constant. Resistance is the opposition to current flow. So if voltage is kept constant, the higher the resistance is, the lower the current will be.

e.g. 6Ω = 24V/4A           8Ω = 24V/3A

Here resistance has been increased slightly, voltage has remained constant and current has dropped slightly.

Middle

The type of material will affect the amount of free electrons, which are able to flow through the wire. If the atoms in the material are closely packed then the electrons will have more frequent collisions and the resistance will increase. There are more electrons in a good conductor

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 is directly proportional to the resistance increase.

Thickness of wire: If the wires width is increased the resistance will decrease. This is because of the increase in the space for the electrons to travel through. Due to this increased space between the atoms there should be less collisions therefore less resistance. The thicker the wire, bigger the surface area.

Current: This affects the resistance because it is opposite to resistance. In this experiment we will keep the current constant.

Conclusion

This is how I intend to carry out the experiment:

Method: First of all I will set up the equipment as shown below:

There will be crocodile clips coming from the

voltmeter and they will define the length of

wire each time. Along the meter ruler, there

will be wire and the crocodile clips will simply

be spaced further apart when required to

make the length of wire longer each time.

When equipment is set up, first length will be set up (from 10cm of wire to 60cm) and current (kept constant) will be chosen. When length increases, we will use the variable resistor to realter the current to its original value. I will record my results in a table clearly stating the lengths of wire used, constant current value, voltage and finally the working out of resistance using Ohm’s Law.

We will take 3 readings of the voltmeter for each length and then work out an average of resistance. This gives us more accurate results because things might have gone wrong with the experiment.

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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