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# I hope to find out how resistance of a wire is affected.

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Introduction

Jason Berry 11H

INVESTIGATION TO SHOW THE EFFECTS OF THE RESISTANCE OF A WIRE

Aim: - I hope to find out how resistance of a wire is affected.

Prediction: - I predict that as the length of the wire increases the resistance will also increase.

## Scientific Knowledge: -

A wire is a bundle of metal strips coated in plastic. The plastic can vary in colour and connect to different terminals

## These are: -

• Black = negative terminal
• Red = positive terminal
• Blue = neutral terminal
• Green and yellow = earth terminal
• Brown = live terminal

The material varies because it has free electrons, which are able to flow through the wire. The number of the electrons depends on the amount of electrons in the outer energy shell of the

Middle

Ω).

Ohm's Law

The law actually says that the resistance of a metal conductor is the same whatever the current - unless it’s getting hotter. However most people think of these equations when the law gets mentioned:

V = IR

V is Voltage in Volts, I is Current in Amps and R is resistance in Ohms.

If the length of the wire is increased then the resistance will also increase as the electrons will have a longer distance to travel and so more collisions will occur. Due to this the length increase should be proportional to the resistance increase. If the wires width is increased the resistance will decrease. This is because of the
increase in the space for the electrons to travel through.

Conclusion

• D.C (Direct Current) is where the current always flows in the same direction. Cells and batteries supply a D.C. current.

Method

1. Set up the circuit as shown above WITH THE POWER SWITCHED OFF
2. First use a piece of wire of one meter in length then move the crocodile clips towards each other to the appropriate length; 90cm, 80cm 70cm, 60cm, 50cm, down to 10cm. This means you will have 10 results.
3. Turn the power on to 2 volts, then take a reading of the ammeter and the voltmeter
4. Before shortening wire to 90cm, allow two minutes for the wire to cool down because it will be very hot to touch and it would also be a unfair test.
5. Repeat the above until length is 10cm
6. Repeat the whole investigation for Reliability

This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.

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