Investigation to test how the length affects the resistance of a wire

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Stephanie Clayton 11 S 2

Investigation to test how the length affects the resistance of a wire

In this piece of coursework I will be investigating the resistance of a wire while current is flowing through it.

To make a current flow through a conductor, there must some potential difference and voltage across it. Different types of wires have different amounts of resistance, for example nichrome wire has more resistance than copper wire

Resistance is what slows down the electrical current in a wire. Resistance is a measure of how hard it is to get a current through a component at a particular potential difference or voltage. Resistance can be calculated by using an equation:

Resistance = potential difference across conductor

                   current through conductor

There are some factors that affect resistance these are:

Length-doubling the length of a wire doubles its resistance

Cross-sectional area-halving the ‘end on’ area of a wire doubles its resistance. So a thin wire has more resistance than a thick one.

Material-a nichrome wire has more resistance than a copper wire of the same size.

Temperature-for metal conductors, resistance increases with temperature. For semi-conductors, it decreases with temperatures.

There is a heating effect whenever a current flows through a resistance. This principle is used in heating elements, and also in the filaments of bulbs. The heating effect occurs because electrons collide with atoms as they pass through a conductor. The electrons lose energy. The atoms gain energy and vibrate faster. Faster vibrations mean a higher temperature.

In the 19th Century there was a scientist called George Ohm who first investigated the electrical properties of wires and created a law named after himself, ‘Ohm’s Law’. Metal conductors obey Ohm’s law, provided their temperature does not change. Put another way, a metal conductor has a constant resistance, provided its temperature is constant. This is not always the case with other types of conductor.

Prediction

My prediction is that the longer the length of wire the more resistance produced, because the electrical current passes through the wire it takes more work the longer the wire for the particles to pass through.

I stated this theory in my introduction to the investigation when I talked about the heating effect of the wire and the effects on resistance when the amount of current that flows through the wire is increased. When the electrons collide with atoms as they pass through a conductor although the electrons lose energy the atoms gain energy and vibrate faster. The vibrations will increase at a faster rate, which causes an increase in temperature.

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Apparatus

Voltmeter                                    Ammeter

Wires                                          Power pack

Crocodile clips

Preliminary Diagram

Preliminary Method

  • I will start by setting up the apparatus and connecting the wires to the piece of wires, voltmeter, and ammeter.

  • Attach the crocodile clips the wire but do not change the length of the ...

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