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An investigation into how the length and thickness of a wire affects its resistance.

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An investigation into how the length and thickness of a wire affects its resistance.


To investigate how two variables, length and resistance affect resistance in a wire.

Background Information

Electricity is a form of energy caused by charged particles. An electric current is a flow of electrons. Electricity can only travel if there is a complete circuit. A power source is needed to give energy to these particles so that they can flow. Cells and batteries act as charge pumps; if several cells are connected they produce a high current. The more cells connected the more charge is produced. The size of a current is the rate at which a charge is flowing and it’s measured in amps with an ammeter. Charges are given energy as they pass through a cell or battery. The higher the voltage of the cell or battery, the greater the amount of energy that is given to the electrons. You can measure the energy given by a cell or battery by using a voltmeter. A voltmeter may be connected around any component that is connected to a circuit. image00.png

Resistance is a force which opposes the flow of electrons around a circuit so that energy is required to push the electrons around the circuit.

Resistance is measured in Ohms.

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Material of the wire – Although in this experiment all of the wires that will be tested are of the same material (nichrome), the material of a wire also determines how much resistance a wire puts up. For example, copper is a better conductor of electricity than iron so it will have less resistance. But in this experiment all of the wires used will be the same material, nichrome.

Nichrome is an alloy of two metals, nickel and chromium.

In conclusion, a short, thick, cold wire would make a better conductor and would have a smaller resistance compared to a long, thin, hot wire which would have more resistance. However in this investigation, I will be investigating how length affects the resistance of a wire. The variable will be the length; however the thickness of the wire will remain the same.


I predict that in this investigation, the wire which is thick or shorter in length will have a smaller resistance than a wire that is thin or long. The diagram shows how if the variable was to investigate the thickness of the wire there would be a greater surface area across the cross-section of the nichrome wire, which means that

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6) Now take the crocodile clips off the wire that is 0.1m long and connect to the wire that is 0.2m long.

7) Repeat step 5 but with move the crocodile clip to 0.3m, 0.4m, 0.5m, 0.6m, 0.7m,, 1m.

8) Record the results.

9) Repeat the experiment for each distance 2 more times.

10) To work out the resistance of the wires, ohms law must be used. This is

 Voltage ÷ Current.

11) Put the ammeter readings, the voltmeter readings, and the resistance in a table.

12) Record the results in a graph.

Results table and Graph on next page


To conclude my prediction that “the wire which is thick or short will have less resistance than a wire that is thick or long” was right. Ohm's law of resistance says, the current flowing through the circuit is directly proportional to the voltage applied.

My prediction was correct, because as the electrons flow through the wire at a steady speed they must slow down when they come to a different piece of wire. When the electrons move flow through the wire they must squeeze together so they can flow successfully through the wire. If the wire is too narrow, the electrons would have a harder time getting through the wire and it would take longer, therefore there is more resistance. However if the wire was thicker the electrons would find it easier to flow and, it would take less time to get to the other end of the wire so there is less resistance.

...read more.

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