Investigating how the length of wire affects the resistance

Topics: Electrical measurements, Volt, Ohm's law Pages: 3 (552 words) Published: December 10, 2003

Risk Assessment:

* I will handle the power supply carefully.

* I am going to only use a maximum voltage of 2 volts.

* I will be careful when handling the mains equipment.

* I will make sure I have a clear space to work in and nothing on the floor around me.

In this investigation, I will set up a simple circuit to be able to read the voltage and current when the length of wire changes, so I then can work out the resistance. I will be using constantan wire starting of with 1m length and then decreasing it by 0.10m intervals down to 0.20m long. I will not go above 1m or below 0.20m because it may be too long that they resist so much current that the wire burns, or the length of the wire is so small that it doesn't resist any current at all. The length of the wire will be changed by moving the crocodile clip across the wire on a ruler. The independent variable will be the length of the wire because that is what I will be changing. The dependant variable will be the resistance because it will change only due to the length of wire.

The circuit should be set up as in the circuit diagram below. It is important that the voltmeter is set up in parallel and the ammeter in series.

Circuit Diagram:

I will work out from the readings of the voltmeter and ammeter the resistance in the circuit. This can be done using the formula:

R=V/I Where R= Resistance, V= voltage, I= Current.

This means I can find and record the resistance. This will work out the resistance in ohms.


* Power supply

* Constantan Wire 1m

* Voltmeter

* Ammeter

* Metre ruler

* Crocodile Clips

* Calculator

* Connecting Wires


I predict the resistance will be at its greatest when the wire is at its longest. This is due to free moving electrons being resisted by the atoms in the wire. In a longer piece of wire, there would be more atoms for the electrons to collide with and so the resistance would be greater. I believe...
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