Physics

Electricity has three features that include current, voltage and resistance. Current is the flow of electrons round a circuit that is measured by the ammeter in amps (A). Whilst the voltage, refer to as potential difference, is the driving force that circulates the current around the circuit that acts like an electrical pressure. The unit of measurement for this is Volts (V), which is measured by a voltmeter. Resistance is a force that slows down the current; consequently it slows down the flow of current. This is measured in Ohms (W).

Between the voltage and resistance there is equilibrium, where the voltage impels the current, whereas the resistance is opposing this electrical pressure. The relative sizes of the voltage and resistance decide how big the current will be. Increasing the voltage allows more current to flow, whilst increasing the resistance would decrease the amount of current flowing round the circuit.

Discovered by George Ohm in 1826, the current is in direct relative amounts to the potential difference. If the temperature is kept constant as well as other conditions, Ohms law is obeyed. The graph on the side illustrates the current through a resistor is proportional to the voltage. V=IR gives the formula for Ohms law.

In order for current to flow it requires electrons to carry the electric current. The electrons are the negative charge that can freely move about. Within metals there are a sea of electrons that can carry the electric current, which is reason why they conduct so well and are used for many purposes, such as wires.

Factors

During the investigation there will be many factors that will affect the resistance in a wire. These factors include:

* Length of wire - If the wire length increases, the distance for the electrons to pass through would take a longer period of time since the electrons collide more with atoms of the wire. As a result there is an increase in resistance as the number of collisions cause the electrons to flow slowly, which justifies the term for resistance. Conversely if the length of the wire is shortened, the time taken for electrons

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