Investigating one of the factors that affects the current in a wire.
In this investigation I will be examining a factor that affects the current in a wire. It is a free choice to what factors I choose to investigate but it must show how it affects the current in a wire and why.
Scientific Knowledge
As any other material metal (wires) consist of millions of atoms. Every atom is surrounded by a number of outer shells. Each outer shell will contain a number of electrons in it. Depending on the type of material the number of outer shells and the electrons within it will vary.
Metals conduct electricity because they have free flowing electrons. However different metals will have different number of electrons and therefore the conductivity of the metal will vary.
The current travels within the wire by hitting the electrons. Once one of the electrons is hit it moves and hits another. This causes a chain movement we call this free flowing current. The current is pushed by voltage. The higher the voltage the harder the electrons are pushed and therefore the current travels faster. Suppose the distance the electrons have to travel is longer then the electrons will have a harder time moving jumping from one atom to another over a longer distance i.e. there is more resistance.
Free flowing electrons conduct the current. How fast they flow (for a particular voltage) is affected by the resistance. In this experiment I will be investigating what effects resistance in a wire.
Predictions
As I have described above the resistance of a wire depends on the number of free electrons. If the number of electrons increases there will be a higher voltage needed to push the current through. George Ohm discovered that the current flowing through the circuit is directly proportional to the voltage applied to the circuit. This means that if you triple one, you triple the other. He also discovered that a circuit sometimes resisted the flow of electricity. The first Ohm’s law states this clearly:
V = I x R
Some variables that will be relevant to this investigation are
- Length
- Temperature
- Material
- The cross sectional area
The Length of a wire
I predict that length will be one of the most important variables. If the length of a wire is increased the number of free flowing electrons is also increased and therefore the resistance will rise.
Temperature
I predict that the temperature will have an effect on the resistance of a wire. As temperature of a metal increases the free flowing electrons gain more energy this causes them to move faster. As they move faster and have more energy a higher voltage is needed to push the current through the wire, so I can conclude that a rise in temperature will cause a rise in resistance. The smaller the length of wire the hotter it will get because more current is flowing through small length of wire.
