# How the length of nichrome wire affects the resistance

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Introduction

Aim:

To show how increasing/decreasing the length of nichrome wire affects the resistance.

Scientific knowledge:

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 circuit itself can resist the flow of particles if the wires are either very thin or very long.

E.g. The filament across a light bulb.

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.

The ohm’s law shows the relations between current (I) and voltage (V) in a conductor.

As potential difference increases/decreases in the conductor, so does the current. This means that the potential difference is proportional to the current.

This is the equation used to calculate voltage, current and resistance:

V

I X R

To work out the voltage: current x resistance

To work out the current: voltage / resistance

To work out the resistance: voltage / current

Ohm’s law is shown as: V = IR

The length of a wire:

Middle

(A)

Voltage

(V)

Resistance

(Ω)

Type of wire

0

0

0

0

N

I

C

R

O

M

E

S

W

G

2

4

5

1.75

1.4

0.8

10

1.01

1.75

1.73

15

0.76

1.85

2.43

20

0.62

1.9

3.06

25

0.5

1.95

3.9

30

0.43

2

4.7

35

0.38

2

5.3

40

0.33

2

6.1

The preliminary test shows:

As the length or the wire increases, the current decreases.

As the length of wire increases, the voltage increases but after 25cm, the voltage stays at 2v.

As the length of wire increases, the resistance increases.

The preliminary test shows what I had predicted.

In my main test I will take the reading of each length 3 times which will give me more accurate results.

I will need a better wire

Conclusion

This experiment proved that my prediction was correct. As the length of wire increased the resistance increased too.

Evaluation:

Overall I think my experiment went as planned. My results were reliable because I made the experiment fair by measuring the wire accurately with a ruler and switching the power supply off each time I took the readings.

I have enough results to reach a conclusion because there is a pattern in my results. It shows how the length affects the resistance in the wire.

I had 1 reading which did not follow the pattern on the graph. I think this happened because we needed to let the wire cool down, the rest of my results were very accurate and reliable.

If I did this experiment again, I would use a new resistance board so the wire will be straight and the results would be more accurate. I would also use a more accurate voltmeter and ammeter, and I will wait a bit longer for the reading.

By doing this experiment, I found out how current, voltage and resistance are related. I also found that the longer the wire, the more the resistance and the shorter the wire, the less the resistance.

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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