The resistance of a wire.

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Prediction
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 number of atoms will also double resulting in twice the number of
collisions slowing the electrons down and increasing the resistance. My graph should show that the
length is proportional to the resistance.
The diagrams below show my prediction and should explain it more clearly:
  Conclusion
In my prediction I said that :
¡§¡K.if the length increases than the resistance will also increase in proportion to the length.¡¨
From my graph I have shown that my prediction was correct, as the Line of Best Fit is a straight line proving that the resistance of the wire is proportional to the length of the wire.
The length of the wire affects the resistance of the wire because the number of atoms in the wire increases or decreases as the length of the wire increases or decreases in proportion.

The resistance of a wire depends on the number of collisions the electrons have with the atoms of the material , so if there is a larger number of atoms there will be a larger number of collisions which will increase the resistance of the wire. If a length of a wire contains a certain number of atoms when that length is increased the number of atoms will also increase.

Conclusion
The way I got my results were fair, I controlled temperature, voltage, length of wire, and the resistance in the circuit.
My results were all accurate, I didn´t get any anomalous results at all because by taking more than one result then calculating the average increases the reliability. But using a rheostat would create even more accurate results, by checking my results with formulas from text books it proves my results are accurate enough to support a firm conclusion that resistance is proportional to the length of the wire. To improve the experiment next time I do the experiment I will use different thickness´ of wire, different materials of wire, use a rheostat or use a variable resistor.
But overall my experiment succeeded the way it was expected to.

I predict that the longer the wire, the higher the resistance. This is because in a longer wire, there are more wire particles that electrons can bump into. Resistance is caused by electrons colliding with wire particles. If there are more wire particles, the chance of an electron colliding with a wire particle will be higher.

In a longer circuit, it is more of a struggle for electrons to get around the circuit without any collisions. There are many more wire particles (acting like obstacles) to avoid. Electrons cannot increase or decrease speed, but they can collide. They collide with the particles in the wire, therefore less electrons are able to flow than in a shorter length wire. As a result, the ammeter shows a lower current with the same voltage. In a short circuit are less particles of wire. This means less collisions and a lower resistance. I have illustrated this below.

Resistance is caused by collisions – more collisions means more resistance. The reason for these collisions is that in a longer piece of wire, there are more free electrons in the actual atoms of the wire that can carry electricity. When there is an electric field the loose electrons escape towards the positive charge (opposites attract). I have illustrated how the electrons escape the atoms below.

In preliminary work, I wanted to find out which factors affect resistance. In some research I found that there were four factors: temperature, cross-sectional area of the wire, resistivity and the length of the wire. I wanted to find out how exactly each factor affects resistance in a wire. However, before doing this I had to see how resistance varied with potential difference, or I would not know what changes I am going to look out for. I found out that as the potential difference increased, the current increased. P.D. and current were directly proportional to each other.

The formula is potential difference ÷ current, or V/I. It is a constant, and is known as resistance. Length however (among other factors – temperature, cross-sectional area of the wire and resistivity as I stated before) affects resistance in that it increases it as the length itself increases.

Varied resistance occurs due to a condition being changed. For example, in this experiment I will change the length of the wire. By increasing the length of the wire, I am creating more collisions between free wire particles and electrons. This means that more electrons are resisted by the wire, resulting in less current. This has changed one of the things out of V/I (current) and therefore resistance (otherwise known as V/I and usually a constant) will vary. How it will vary is as simple as this: the longer the wire the higher the resistance.

Ohm’s law states that a current flowing through a metal conductor is directly proportional to the voltage across its ends (provided all other conditions are constant). So I know that if we add a variable – in this case length – resistance will change. I expect that the longer the wire, the higher the resistance.

Potential difference is what “pushes” electrons around a circuit. When a wire has more electrons, for the same voltage it produces less current, meaning that there is more resistance. For example, say 6V are being put through a wire, and it produces a current of 3A, we can work out the resistance of this wire by using the formula V/I. 6 ÷ 3 = 2Ω. Now, if we put the same voltage through the same wire, only shorter, it might produce 2A of current. 6 ÷ 2 = 3Ω. So now the resistance would be more, because the current is less. Fewer electrons would be able to flow through the wire, and electron flow is the same as current.

I predict that with a wire length of 0.1m, the resistance will be lowest. I say this because in such a short wire there are not so many particles for passing electrons to collide with. You could compare it to a high street that you are walking down. In the time that you walk down a longer high street you would encounter more obstacles (in the form of people in this case) than you would in a shorter high street (this is assuming the streets are as busy as each other). It is the same with electrons. If they must travel further round the circuit, they will have to avoid a lot more wire particles. They will obviously collide more, producing less electron flow (otherwise known as current).

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I predict that at 0.2m the resistance will be higher than that of 0.1m, because of reasons previously stated. There will be twice the amount of wire particles (as 0.2 is twice 0.1), which should technically mean that there would be twice the amount of collisions. Although we cannot measure the amount of collisions, we can measure the resistance and I would expect this to be higher than that of 0.1m.

I predict that the resistance will increase steadily as the length becomes greater (i.e. 0.3m’s resistance will be more than in 0.2m, increasing in 10cm increments up to 1m, ...

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