Electric current is the movement of electrons through a conductor. In this experiment the wire will be the conductor. When resistance is high, conductivity is low.

Science Theory:

Electric current is the movement of electrons through a conductor. In this experiment the wire will be the conductor. When resistance is high, conductivity is low. Metals conduct electricity well because the atoms in them do not hold on to their electrons very well. Free electrons are created, which carry a negative charge, to ‘jump´ along the lines of atoms in a wire which are in a web structure. Resistance is when these electrons, which flow towards the positive from the negative, collide with other atoms, they then transfer some of their kinetic energy. This transfer on collision is what causes resistance. So, if we double the length of a wire, the number of atoms in the wire doubles. This increases the number of collisions and energy transferred twice, so twice the amount of energy is required. This means the resistance is doubled. Therefore this energy collision causes electrical heating. So we can relate this and say that the resistance is proportional to the length:

So we can know say that the thicker the wire the less amount of resistance will occur. As there is a bigger area for the charges to travel through will less chance of collisions. Therefore it is true to say that the resistance is inversely proportional to the area (cross sectional area). And therefore put this into the equation

R I/A

So putting this all-together will gives us the equation

R = pL/A so we can now use this equation to work ...

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R I/A

So putting this all-together will gives us the equation

R = pL/A so we can now use this equation to work out the predicted results, as shown in the prediction.

Where “p” is a constant for a particular material at a particular temperature, “L” is the length and “A” is the cross sectional area.

Consequently rearranging the formula gives:

p=RA/L

Some wires have different thicknesses. In those wires the particles are spread out a lot more with gaps between each particle. With these gaps there is less resistance because there is more space for the electron to pass through.

This is how the particles are spread out in a thick wire. As you can see it is a lot of space for the electrons to pass through therefore the a thick wire has less resistance whereas a thinner wire would have more because its particles are more like this.

The particles in the thinner wire are closely packed together and hardly any space to for electrons to pass through therefore it has a higher resistance.

Prediction

Most metals are closely packed - that is, they fit as many atoms as possible into the available volume. Each atom in the structure has 12 touching neighbours. Such a metal is described as 12-co-ordinated.

Each atom has 6 other atoms touching it in each layer.

There are also 3 atoms touching any particular atom in the layer above and another 3 in the layer underneath.

This second diagram shows the layer immediately above the first layer. There will be a corresponding layer underneath.

This relates back to the theory that if you double the length of the wire, the numbers of electrons jump and so energy required doubles as well. The electrons will have double the distance to travel so the resistance will double.

If this prediction should be true, the graph should be a straight line going through the origin, as current is proportional to the voltage, hence the resistance “I=V” is constant showing that the wire is an ohmic conductor.

As shown in the scientific knowledge the predicted results can be worked out by using the formula R=pL/A. given that you know the length, resistivity of the wire, which is 100 x 10ˉ8, and cross sectional area of the wire. So you can therefore work out the predicted resistance. Also referring to the science theory the thickest wire will have the least resistance and the thinnest wire will have the most resistance