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# To discover how a current through a metal wire depends across its ends.

Extracts from this document...

Introduction

Rumel Ahmed 3873

OHMS LAW

Aim- To discover how a current through a metal wire depends across its ends

Every element on this planet is made up of tiny particles called atoms.  An atom consists of 3 things.  The first are neutrons.  Neutrons have no charge at all and are located in the central bit of the atom.  The second are protons.  They have positive charges.  Along with the neutrons they form the nucleus.  Around the nucleus there are electrons they have a negative charge, they orbit the nucleus in shells.  The first shell has only 2 electrons then the rest of them can hold up to a maximum of 8 electrons (see below).

## Proton (Positive)

Neutron (No Charge)

Electron (Negative)

In metals the outer electron are held very weakly to the atom and often wander away, they are called conduction electrons.  When an electric current is passed across a wire one end becomes negative and the other becomes positive.  The conduction electrons are negatively charged so naturally they would move towards the positive end.  But as these electrons move along the wire, atoms would obstruct their progress along the wire thus slowing them down.  This is called resistance.  Resistance will only occur if there is a current, and a current will only flow if there is a voltage.

Resistance is measured in Ohms, named after the scientist that discovered this.

Middle

Nichrome wireClips (4)Normal wireRuler

I have used a voltmeter so I can record down the voltage and an ammeter to record down the current.  With this knowledge I can use the formula that I showed at the beginning to work out the resistance.  I have to use a variable resistor because if I don’t the wire heats up and burns.

This is a diagram of the experiment.

Method

• Set up the apparatus as above, according to the diagram.
• Set the power pack to D.C
• Change the length of wire at an interval of 10 cm.
• Do the experiment twice and work out the average, this will make the results more accurate.

Conclusion

##### Evaluation

The results were quite accurate because I had done the experiment twice and got an average from the two results.

There are quite a few factors that could affect the results of the experiment. Some of these are variables that were mentioned earlier and could not be controlled, or they were variables that were not initially considered.

While performing the experiment, the temperature could have changed and that would have made the results really useless.  Even a change of 1°C could effect the results, I am not entirely sure if that happened or not but the results seem pretty fine.

Also a combination of human error and faulty equipment could render the experiment a failure.  Sometimes people rush things and takes down a wrong reading and also faulty equipment can sometimes give wrong readings.

The method of the experiment could probably also be improved to obtain more reliable results.

Due to the nature and convenience of the experiment, it could be easily modified to investigate another factor. I investigated the length when I could have investigated the cross width or the temperature, by investigating them I could have got better results but controlling the temperature would have been really difficult, putting in all that effort might not have been worth it.

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