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Find out if there is a relationship between the length of the resistance wire and the value of resistance by using different lengths of resistance wire.

Extracts from this document...

Introduction

Problem: We aim to find out if there is a relationship between the length of the resistance wire and the value of resistance by using different lengths of resistance wire.

Background knowledge

Wires that don’t let much current pass through them are called resistance wire. Resistance wires are used to control the amount of current flowing through a circuit-resistance is measured in ohms ().

Some wires are more resistant that others e.g. nickrome and constantan. This is due to the arrangement of the atoms in the wire; the atoms are arranged so that it is more difficult for the free electrons to move through it therefore electric current cannot flow as well. Also resistance wire tends to heat up, as the free electrons need more energy to move through the wire.

To find resistance we use the equation:

Resistance = voltagecurrent           or          R= VI

If a graph of voltage against current is a straight line passing through the origin then the current is directly proportional to the current flowing- this result is called ohms law and applies to metallic conductors at a constant temperature.

Variables-things that might affect the resistance

1.        Length of wire

2.        Thickness of wire

3.        Temperature of wire

4.        Type of wire

Variable to investigate

...read more.

Middle

Length of resistance wire (cm)        

Voltage

(V)        

Current (amps)        

Average

(Amps)        

Resistance

R=VI

()        

                1        2        3                        

50        

        60        

70        

80        

90        

Sample Graph

Safety

1.        Make sure the circuit is checked by teacher before you start experiment

2.        Keep all chairs and bags under table

3.        Do not let wire heat up too much.

Obtaining Evidence

...read more.

Conclusion

Yes my conclusion supports my prediction because I predicted that the longer the wire the greater the value of resistance and it is clear from my results this happens.

Are your results reliable?

I think my results are quite reliable because in the graph 3 out of the 5 points lie on the line.

There are 2 anomalies but they are only just off the line and I think they might have been caused by either:

1.        Inaccurate reading of ammeter

2.        Length of wire not accurate

3.        Bumps in wire

4.        Crocodile clips not in the right place

Could you improve your experiment in anyway?

The experiment could have been improved by using new resistance wire for each length instead of using the same piece each time because when you uncoil the wire it is not completely straight so affecting the results. Also I could have left a more accurate amount of wire for the crocodile clips to go on, as 1cm at each end could have been too long.

Are your results reliable enough to make a firm conclusion and convince others?

I think that my results are reliable enough because in the graph only 2 points lie off the line and they are very close to the line which shows there wasn’t much error so I think they would convince others.

Ashlene Clarke

...read more.

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