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# My aim is to investigate how the resistance of a piece of resistance wire depends on length and also to find the length of wire needed to make the required resistors.

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Introduction

Physics Investigation (Coursework)- GCSE

Aim-

An electronics factory needs resistors of 5 ohms, 10 ohms and 15 ohms for a new electrical device. My aim is to investigate how the resistance of a piece of resistance wire depends on length and also to find the length of wire needed to make the required resistors.

## Introduction-

My investigations main topic is resistance and how a length of a resistance wire affects the resistance. A selection of different wires made from constantan and nichrome will be available for me to use,

Wire A – constantan wire of approximate diameter 0.3mm

Wire B – constantan wire of approximate diameter 0.4mm

Wire C – nichrome wire of approximate diameter 0.3mm

Constantan is an alloy whose resistance stays fairly constant when it becomes hot. In fact the resistance changes by less than 0.5% even when the temperature rises by a few hundred degrees.

Nichrome, along with other metals, is an alloy whose temperature does change appreciably when it becomes hot.

## Resistance-

With a given energy source, such as a battery or a generator, the size of current that flows is decided by the resistance of the circuit. All conductors resist the flow of electric charge to some extent, but some are better at it than others. The bigger the resistance of a conductor the harder it is for electric charge to flow through it. For a given voltage applied to it, the current would be less.

Middle

In a short wire electrons can travel to the opposite side quicker as there is a shorter distance and less ions to pass. In a long wire electrons take longer to reach the opposite side, as there is a longer distance to travel. Also there will be more ions present, so it will be harder for them to pass through and there will be more collisions, which results to more energy in electrons. Therefore as the wire gets longer the resistance increases.

## Width of the wire-

#### Width of wire affects resistance. If the width is increased the resistance will decrease. This is due to the increase in the space for the electrons to travel through. Due to increased space between atoms there should be less collisions. Below is a diagram to explain this-

In a thin wire there are less metal ions, so therefore there are less routes for the electrons to travel through. So it takes longer for the electrons to get around, therefore resistance increases. In a thick wire there are more metal ions, so therefore there are more routes for the electrons to get around. There are more routes so therefore it takes a shorter time for electrons to get around. So the current increases and resistance decreases.

## Material of the wire-

Material of wire can affect resistance.

Conclusion

I will then double check everything before I turn on the power pack as electricity is involved.I will not touch the wire, as it will be hot.I will not keep any of the equipment near the water tap.I will make sure no equipment is near the edge of the workbench.If any danger is in place with electricity I will make sure I go on turn the electricity off from the mains.

Method (final experiment)-

• I will clear the workbench and collect all the equipment.
• I will set all the apparatus out on the workbench appropriately.
• Clear things near the workbench, (example-bag)
• I will get my power pack and plug it in, and put my meter ruler straight.
• I will connect the circuit with the crocodile clip wires, ammeter and voltmeter.
• I will straighten the constantan wire, and put it straight on the ruler, then tape it so it doesn’t move.
• I will put one crocodile clip on one end of the ruler where it will stay still constantly through the experiment.
• One crocodile clip will move down the ruler to each measurement.
• I will draw the results table up.
• Before I start the experiment I will make sure everything is working to plan and all the apparatus is working.
• I will then repeat the whole experiment two more times.

This is what my results table will look like-

 Length of wire(Cm) Voltage (Volts) Current (Amps) Resistance (Ohm) 20 40 60 80 100 120 140 160 180 200

Below is a diagram of my apparatus-

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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