Investigate the effect of changing the length of a wire on the current flowing through it.

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Aaron Atkinson 10/68                GCSE Physics: Coursework

GCSE PHYSICS COURSEWORK:

MODULE 5 ENERGY & ELECTRICITY

Investigate the effect of changing the length of a wire on the current flowing through it.

Skill Area P: Planning

        This coursework assignment deals with the relationship between the length of a wire and the current flowing through it. I will refer to other factors that determine current so that I can use scientific knowledge and understanding to turn ideas into an appropriate strategy. It is important to understand what current is to progress with the investigation.

-         Electricity is a flow of charged particles, which may be electrons or ions

  • Current is the measure of the rate of flow of electrical charge. Electric current is measured in amperes, A. The ampere is defined in terms of the magnetic effect of an electric current.
  • Electric charge is measured in coulombs, C. One coulomb is defined as the amount of charge passing a point in a circuit each second when the current is one ampere.
  • Current will only flow through a component if there is a voltage across that component.
  • The equation for current is defined as: I = V / R where I = current, V = voltage or potential difference or p.d., R = resistance.
  • Voltage is the “push” or energy given to the charges (usually electrons).
  • Ohm’s Law states that the current through a metallic conductor at constant temperature is proportional to the voltage.
  • Resistance is measured in Ohms (symbol Ω). It is a measure of how much the current is slowed down. The bigger the resistance, the smaller the current.

There is of course a balance between voltage and resistance. The aim of voltage is to push the current around the circuit, and the resistance is opposing it – the relative sizes of the voltage and resistance decide how big the current will be:

INCREASE in VOLTAGE  INCREASE in CURRENT

INCREASE in RESISTANCE  DECREASE in CURRENT

If the resistance of a component is constant (stays the same) for different values of V and I, then a plot (graph) of V against I will be a straight line. The gradient (slope) of the line shows how big the resistance is.

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There are also other factors that affect current:

  • Material
  • Temperature
  • Thickness

Material – Certain types of materials have a greater resistance than others.

Temperature – an increase in temperature results from an increase in voltage, and essentially an increase in current. From this we can deduce that at high temperatures the resistance is lower.

Thickness – A wire with a greater thickness has a larger diameter for the electrons to flow through. This means there is more space for them to flow freely. The result  Resistance decreases.

In general:

Increase in voltage  increase in ...

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