Structure of a Wire
A wire is made up of positive ions and negative electrons. When the
voltage is on, the electrons try to push in between the ions. The ions
DO NOT MOVE. They are lined up. The electrons carry the current, which
is measured in Amps. The voltage charges up the electrons, which is
the then, the driving force of the electrons. When the voltage is on,
resistance is caused between moving electrons and ions; energy is lost
during these collisions.
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Collisions:
The picture below is a model of charge moving from a wire to the lamp
filament. The filament is thinner, and has fewer conducting electrons,
than the same length of conducting connecting wire, so the charge has
to move faster to have the same flow. The filament heats up because
the electrons transfer their energy in collisions. The more
collisions, the more energy transferred, so the greater resistance.
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Aim:
To investigate how the length of a wire affects the current that flows
through it.
Prediction:
I predict the longer the wire, the more resistance caused to the
current. The electrons in a longer wire would collide with the ions
more often in a longer wire, and would slow the current. I predict the
shorter the wire, the less resistance caused to the current. There
would be less electrons colliding, and would increase the current.
Method:
Apparatus:
110cm constantan wire
Crocodile clips
Voltmeter
Ammeter
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Connecting wires
Power pack
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Longer Wire
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Shorter Wire
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Method:
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V
We set up the apparatus as shown in the diagram. The voltmeter was set
at 3V, in parallel. The ammeter was set up in series circuit.