Resistance of a wire

Essay by maja15High School, 10th grade March 2006

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- Set p the equipment as shown on the diagram.

- One meter length of wire is fixed to a one meter ruler.

- The first crocodile clip is clipped to the wire at the 0cm position on the one meter ruler.

- The second crocodile clip is clipped to the 10cm position.

- The power supply is turned on. The voltage and current are then read of the ammeter and voltmeter, and recorded.

- The power supply is then turned off and the second crocodile clip is moved to the 20cm position.

- Then the power supply is turned and you record the readings from the ammeter and voltmeter.

- Then you turn the power off and move the clip to the next position, you do that until you get to 90cm then you stop.

- After you do that, it is best to repeat the same thing from the beginning at least three time to get fair and accurate results.


Current can easily pass through a piece of copper connecting wire. It does not pass trough as easily in a thin nichrome wire of an electric fire element. This wire has much more resistance. Energy has to be spent to force electrons through it. And heat comes off as a result.

All conductors have some resistance but:

- Long wires have more resistance than the short wires.

- Thin wires have more resistance than thick wires.

- Nichrome wire has more resistance than copper wire of the same size.

Resistance is calculated using this equation:




The unit of resistance is the ohm

Here is an example:

If there is a voltage of 12 volts across this nichrome, then a current of 4 amperes flows through.

So: 12

Resistance = ohms