To investigate how the resistance of a wire is affected by various factors

The rate at which electricity flows through a circuit is affected by the resistance of the components and/or wires in the circuit. Increased resistance results in a decrease in the amount of current that will flow through the wire. Good conductors tend to result in low resistance while poor conductors (insulators) result in high resistance.

Section 1: Planning

The purpose of this investigation is to look at the main factors that are responsible for affecting the resistance of a wire in an electric circuit. I have decided to look at four different factors:

• The material
• The temperature
• The cross-sectional area
• The length

From the equipment available, I have concluded that it could not be possible to investigate how temperature affects the resistance of a wire, as there are no thermometers or any other ways of measuring temperatures. Also, it would be difficult to try and keep the wire at a constant temperature while measuring the current and voltage of the circuit. It is also dangerous, as the wire may get too hot and burn the surface where I am working on or just catch alight itself.

Also, as there are only three types of wires (constantan, nickel chrome and copper), it would not be ideal to investigate how the type of material affects the resistance of a wire.

Length / cm

Voltage / V

Current / A

100

0.51

1.14

50

0.42

1.12

90

0.45

1.13

Nickel Chrome Wire, SWG 32

I have decided to use Nickel Chrome, SWG 32 as it seems to be the least dangerous wire to use and also provides me with the most data, because it loses heat the fastest, preventing the wire from becoming too hot too quickly and therefore interrupting the present resistance in the circuit.

Extent and Range

As I have decided that my independent variable for this investigation is the length of wire, I am going to use lengths of wires ranging from 20cm long to 100cm, as this will give me a large enough range to obtain sufficient results for my conclusion. It will be harder to go over 100cm as then two rulers will have to be put next to each other, and this is not at all reliable. The extent for my investigation would be 10 – 20cm, 30cm, 40cm, 50cm, 60cm, 70cm, 80cm, 90cm and 100cm. I will do this in order to find a regular pattern and to do a suitable extent.

I have also decided that the power pack setting will be at a constant of 5V as this is not high enough to start burning the wire but not too low that the readings will be much too small to record.

As I had mentioned before, my best fit line on my results graph shows that there is a good strong positive correlation with the data points all very close to the line, although it was not a perfect line with all the points lying exactly on it. This shows that the reliability of my evidence and my data was very concise and sufficient enough to be recorded.

Any further work I could have done

If I had time, I could have also investigated what else affects the resistance of a current. I could have taken readings for a copper or constantan wire, both at SWG 32 just as I had for this investigation with nickel chrome. That way, I would be able to support my prediction even more with the evidence that I come up with, that this ‘prediction’ works for all metals; that all metals have a direct proportion of resistance to the length of the wire.