AQA additional physics GCSE - Current electricity P2 5

Every component has its own symbol. Theses components are connected to form circuits. A circuit diagram shows this circuit.

Current potential graphs  are used to show how the current passing through a component varies with the potential different across it.

The current is measured with an ammeter. The potential difference is measured with an voltmeter.

The current through a resistor at a constant temperature is directly proportional to the potential difference cross the resistor.

Resistance (ohms) = Potential difference (V) / Current (A)

Below current potential difference graphs for a diode and a filament lamp.

If current connected in series components are connected one after the other so a break would stop the flow of charge.

current = potential difference / total ressistance         or

Potential difference = current x resistance

This can be used to find the individual potential difference of each component.

For components in a series

• The current is the same in each component
• The potential differences add to give the total potential difference
• The resistances add to give the total resistance
• The bigger the ressistance of a components the bigger its share of potential difference

In a parallel circuit each component is connected across the supply, so if there is a break in the circuit the charge supply still continues.

For components in parallel:

• The potential difference is the same across each component.
• The total current is the sum of the currents through each component
• The bigger the ressistance of a component, the smaller its current is.