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# Find out if there is a relationship between the current and the length of wire.

Extracts from this document...

Introduction

#### GCSE Physics Coursework

An investigation to find out how the current changes as the length of the wire changes.

AIM: To find out if there is a relationship between the current and the length of wire.

## P2a. Safety

Before we can go ahead with the experiment it is vital that we check that everything in the experiment is safe. A safety check would include checking that there are:

No loose connections

No sharp wires

No exposed wires

No water around

No power when experiment is not taking place

It is important that we keep these things safe, as it could interrupt the readings or even cause us to have no readings at all.

## P4a. Fair test

I need to keep the experiment as fair as possible.

Things I must keep constant:

We must keep the voltage constant if we use the battery a lot it will get weaker and this will change the current and give false results.

It is important that we use the same wire through the experiment because of different levels of resistance. This would also affect the final results. We will be using constantan wires through the experiment.

A thing I am going to vary:

Middle

Varying cross sectional area of the wire

P6b. Suitable range

For my range of data I will be varying the length of wire by 10cm, from 100cm-10cm doing this I will try to find a relationship between the current and the length of the wire.

Preliminary experiment

In my preliminary experiment I used the following equipment to carry out an experiment as accurate as I can.

Constantan Wire (100cm)

Cell two batteries

Switch

Circuit Wires

Crocodile Clips

Scissors

Meter Rule

Ammeter

I obtained these results:

Preliminary experiment results

 Length of wire (cm) Current (amps) 1000/length 100.0 0.29 10.0 90.0 0.31 11.1 80.0 0.35 12.5 70.0 0.39 14.3 60.0 0.44 16.6 50.0 0.49 20.0 40.0 0.57 25.0 30.0 0.73 33.3 20.0 0.91 50.0 10.0 1.07 100.0

On the next two pages are my graphs for the preliminary experiment, taken from my preliminary results.

Preliminary experiment analysis

The basic trend of my graph (1000/length) is that as the length decreases the current increases and it is in proportion. I am hoping that I will get similar results, but I expect them to be more accurate and hopefully I will find it easier to make a conclusion.

Obtaining

I used the following equipment:

Constantan Wire (100cm)

Cell two batteries

Switch

Circuit Wires

Crocodile Clips

Scissors

Meter Rule

Ammeter

Variable Resistor

Conclusion

Where are the anomalies?

In graph 4, there is one anomaly it is off the line of best fit, I have calculated 1000/length for 11cm (length) to see if my cutting of the wire is wrong.

1000/11= 90.9,                91cm

Therefore this is much more closer to my line of best fit. Therefore I can say that mis-cutting the wire by only one centimetre can have a significant effect later on in my results and graphs.

Ways in which I may of gone wrong:

Inaccurate cutting of wire

Inaccurate results

May not of kept the room temperature at a constant level

The crocodile clips may not been connected to the wire properly

Loose connection

May not of been constant room temperature

Improvements:

· I could also have made the experiment contain more values, e.g. go from 1-5V instead of just 0.50v this would mean I would get more results, and the average result would have been more accurate, as the anomalies wouldn’t affect the results as much.

· An improvement I could have made is to have kept the temperature constant, and made sure of this by keeping the length of wire in a water bath at a constant temperature.

Further Investigation:

• Keeping the length constant but varying the thickness of the wire. Seeing if the resistance or current changes when I use a fat or thin constantan wire.
• I could use different materials like carbon or lead and see if it matters when I change the material.

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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