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# Investigating the resistance of wire.

Extracts from this document...

Introduction

16th October 2001

Investigating the resistance of wire.

Aim: To investigate into how the length of a piece of wire affects the resistance of the wire.

V / I = R

V - Potential Difference (Volts)

I - Current

R - Resistance

Variables:

Temperature - The temperature of the wire being tested will cause the atoms in the wire to

vibrate due to the increase in energy, when heated. This will result in far more collisions

occurring between the electrons and atoms, as the atoms will move more rapidly into the

path of the electrons. Ultimately the increase in collisions will result in the resistance of the

wire being increased.

Wire length - As the length of the wire is increased the distance the electrons have to travel

will also, so more collisions will occur. So the resistance of the wire should generally be

proportional to the distance the electrons have to travel.

Wire material - Depending on the material used the amount of electrons allowed to freely

flow thought the wire will vary. The number of electrons will depend on how many are in the

outer energy shell of the atom. So the larger the atoms of the wire the more electrons will be

present. Also the more tightly packed the atoms the more frequent the collisions will be

increased as will the resistance.

Wire diameter - If the wires width is increased the resistance will decrease as a result of the

atoms being spread out over a wider area, so the space for the electrons to travel though is

increased.

Middle

and voltmeter, and recorded.

5.        The power supply is then turned off and, then the resistance is worked out according

to ohm’s law. V = I / R. These are then recorded in the table.

The above steps are completed for each length, 10,20,30,40,50,60,70,80,90 or 100cm

then the entire investigation is repeated 3 times for accuracy and allowing me to create an

average.

Prediction:

I predict that if the length of the wire increases the resistance will also increase, this should

be roughly in direct proportion to the length. Also I know that the voltage will not change

unless I alter the variable resistor, even then the current will stay in the correct proportion to

the volts. This is roughly what I think my final graph will look like:

As you can see the line of best fit is straight and travels right through the origin.

Hypothesis:

Resistance is a force which opposes the flow of an electric current around a circuit so that

energy is required to push the charged particles around the circuit. The quantity of resistance

in an electric circuit determines the amount of current flowing in the circuit for any given

voltage applied to the circuit, according to Ohm's law. The circuit itself can resist the flow of

particles if the wires are either very thin or very long.

Resistance is measured in ohms. The symbol for an ohm is ?. A resistor has the resistance

of one ohm if a voltage of one volt is required to push a current of one amp through it.

Conclusion

measurements for the length of the wire were inaccurate, this was due to bends and dents in

the wire. So to improve my experiment I could have flattened out the wire more when

measuring as this would increase accuracy.  There are also a number of possible ways I

could expand my experiment. These all involve changing different aspects to the circuit.

*        Wire Width - I would be able to investigate into this experiment by following my

experiment plan, just changing the width of the wire I am testing instead. I believe that

as I increase the width of the wire I will see the resistance decrease. Due to the increase

in the amount of space available for the same amount of electrons.

*        Temperature - I would also be able to investigate into this by following my previous

experiment plan, but changing the temperature that the wire is tested at. I would expect

to notice an increase in resistance as the temperature increases. This is because the heat

causes the atoms in the wire to vibrate, causing more collisions, and more resistance.

*        Material - This would also be done by following my previous plan, although changing

the material used in the wire. This should affect the amount of free flowing electrons. As

the amount of electrons will be affected by the type of material. If the material has a high

number of atoms then the number of electrons will be large too, so more collisions will

occur and therefor a higher resistance is created. The same is also present when there

are fewer atoms in the material.

Bibliography:

www.scienceyear.com

my work book

Britannica Encyclopaedia

Heinemann modular science for GCSE

Encarta Encyclopaedia

Chris Wirt

1

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