- 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.
Resistance = ohms