Investigating the resistance of a wire - looking at variables.

Variables

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, which 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.

Nichrome wire high resistance Copper wire low resistance

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.

Short wire low resistance Long wire high resistance

4.Wire width: If the wires width is increased the resistance will decrease. This ...

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Nichrome wire high resistance Copper wire low resistance

Short wire low resistance Long wire high resistance

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.

Thick wire low resistance Thin wire high resistance

Prediction

I predict that if the length increases then the resistance will also increase. I think this because the longer the wire the more ions and so the more likely the electrons are going to collide with the ions. Therefore, if the length 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 slowing the electrons down and increasing the resistance. My graph should show that the Length is directly proportional to the resistance this should be shown with a diagonal line going up the graph. Also doubling the length is the same as doubling the number of similar resistor so this should obey, Total resistance = Resistor one + Resistor two.

Method

Fist of all I will make sure I carry out my experiment away from water and I will keep the voltage low. I will do this to stop the risk of electrocution.

Equipment

Power Supply,
Ammeter,
Voltmeter,
Just over 100cm of Wire,
Meter Rule,
some Crocodile Clips,
and some Connecting Wires.

I used a variable resistor so that for every distance I could take three readings and then find an average so that it was a lot more accurate. The circuit was set up as shown above. A table was drawn out for the results to be recorded. I decided to set up the circuit with the meter rule selotaped to the table. This will make it easier as I will not have to keep on holding the wire then putting the crocodile clips on. Next, I moved the crocodile clips down twenty centimeters and take the readings of the voltmeter and ammeter and record it on my table. I did this five times moving a further twenty centimeters each time until I got to a meter. I have chosen these lengths because they are easily measured by the meter ruler and give a good range of results. When I got my results I worked out the resistance using the equation.

Resistance= Volts/amps

Results

Interpation

From my results I can see that as the length doubles the resistance also doubles although it is not exact it is pretty close. After carrying out my experiment I now know that as the length of a piece of wire increases the resistance also increases this fits with what I said in my conclusion.

Evaluation

I thought that my results were good but they could have been improved a lot. I could have improved them by using an electronic ammeter and voltmeter because the readings would have been more accurate also I could have held a hairdryer over the wire to keep the temperature the same all the time.

I think that some further work is needed to show that ohms law is true to do this I will need to carry the experiment out again and this time improve it with the points I have mentioned above. It is clear that as the length of the wire increases the resistance increases. On the graph I have produced I drew in a line of best fit and from this you can see that as the length doubles the resistance doubles but although it is not completely accurate I think it is god enough to convince others.