Factors Which Affect the Resistance of a Wire

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Factors Which Affect the Resistance of a Wire

By Richard Roaf

Introduction:

Resistance is a force that opposes the flow of an electric current around a circuit so that energy is required to push the charged particles around the circuit. The circuit itself can resist the flow of particles if the wires are either very thin or very long. e.g. The filament across an electric bulb is quite thin as needs to resist the flow of particles for the bulb to glow.
Resistance is measured in ohms.

George Ohm discovered that the emf of a circuit is directly proportional to the current flowing through the circuit. This means that if you triple one, you triple the other. He also discovered that a circuit sometimes resists the flow of electricity. He called this resistance. He then came up with a rule for working out the resistance of a circuit:

V/I = R

V - Volts
I - Current
R - Resistance.


Apparatus:

Power Supply
Ammeter
Voltmeter

Resistance Wire
Meter Ruler
Crocodile Clips
Connecting Wires


I set up my experiment as shown above.

Extra Background Information :

The total resistance of resistors in series is the sum of the resistance of each one. Each cm of wire has a particular resistance, if you double the length of wire, it is like having two of the shorter wires in series.

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.

Before starting my coursework I have decided to chose a factor that will affect the resistance of a wire. I shall do this by going through all of the factors that affect the resistance of a wire and how I would measuring each factor to find out which would be the most effective and easiest factor to measure.


Below is a list of factors and reasons why they affect the resistance of a wire. From this list of factors I shall only pick one factor to investigate


Factors
1.Temperature:

If the wire is heated up the atoms in the wire will start to vibrate because of their increase in energy. This causes more collisions between the electrons and the atoms as the atoms are moving into the path of the electrons. This increase in collisions means that there will be an increase in resistance.


2.Material:

The type of material will affect the amount of free electrons that are able to flow through the wire. The number of electrons depends on the amount of electrons in the outer energy shell of the atoms, so if there are more or larger atoms then there must be more electrons available. If the material has a high number of atoms there will be high number of electrons causing a lower resistance because of the increase in the number of electrons. Also if the atoms in the material are closely packed then the electrons will have more frequent collisions and the resistance will increase.


3.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 proportional to the resistance increase.


4.Wire width: 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.

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5.Wire area: If the area of the wire is increased then 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. This is similar to the wire width but instead of using different swg’s of wire we will double up the wire.

To chose which factor I am going to investigate I am going to consider how I would measure each factor and which factor would be the best and easiest to record.
To measure the wire width I ...

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