The Electrical Resistance of a Wire.

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The Electrical Resistance of a Wire

Aim

 

I am going to be studying the resistance of wire. The purpose of this investigation is to see how the length of a wire affects the dependent variable, resistance.

My Prediction and Hypothesis

I predict that if the length increases then the resistance will also increase in proportion to the length. I think this because the longer the wire the more atoms and so the more likely the electrons are going to collide with the atoms. So if the length is doubled the resistance should also double. This is because if the length is doubled the numbers of atoms will also double resulting in twice the number of collisions slowing the electrons down and increasing the resistance. I predict this because resistance of a wire is the slowing down of the current electrons in the wire by atoms of the wire. The current is the flow of free electrons along the wire.

I am going to plan an investigation to find out if my prediction is correct. In this plan I am going to set up a circuit to measure the current through a wire and the potential difference (voltage) across it. I will then use the formula resistance =,                       to calculate the resistance of the wire.

Plan

In this investigation a simple circuit will be set up to read the voltage and current when the length of the wire changes. My plan is to find the best results by observing resistance of different sized wires. I will measure the resistance of about 10 different wire lengths using a voltmeter and ammeter. The wires will range from 10cm to 100cm, going up in tens. Each wire will be measured three times and then an average will be noted to ensure accuracy. The same will be done when voltage and amps are measured

Fairness and Accuracy

To ensure that the investigation is carried out in a fair way and that the results will be accurate
and reliable a number of things must be followed. The only variable in the test will be the
length of the wire. The wire must be pulled tight against the ruler and taped in place to ensure
the length is accurately measured. The same circuit and battery must be used throughout as
different batteries may have different voltages if they are old. The experiment should be        
repeated 3 times and an average taken to make sure that the results are reliable. I also need to
make sure that all the equipment is the same so the results are the same and more accurate.
At the start of the experiment I will check that the ammeter and volt meter read zero when the circuit is off. If they are not I will adjust them. To ensure fairness I will keep the thickness and material of the wire the same by using wire off the same reel.

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Scientific knowledge  

Here are the scientific principles behind this investigation with help from physic books.

All materials, solid, liquid or gases are made up of atoms. The atoms themselves consist of a central bit, called the nucleus, made up of particles called protons (which have a +ve electrical charge) and neutrons (which have no charge) Orbiting around the nucleus are electrons which are very tiny and have a -ve electrical charge. E.g.; the electrons orbiting in layers like the rings of an onion, and it's the ones in the very outside layer, the outer ...

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