Parallel Circuits

• Parallel circuits - independance and isolation
• In parallel circuits, each component is separately connected to the +ve and -ve of the supply (except for ammeters, which are always connected in series)
• If you remove or disconnect one of them, it will hardly affect the others at all
• This is obviously how most things must be connected, e.g. in cars and in household electrics
• Everyday circuits often include a mixture of series and parallel parts
• Potential difference in the same across all components
• In parallel circuits all components get the full source pd, so the potential difference is the same across all components: V1 = V2 = ...
• V1 = V2 = ... means that identical bulbs connected in parallel will all be at the same brightness
• Current is shared between branches
• In parallel the total current flowing around the circuit is equal to the total of all the currents through the separate components
• I(total) = I1 + I2 + ...
• In a parallel circuit, there are juctions where the current either splits or rejoins
• The total current going into a junction has to equall the total current leaving
• If 2 identical components are connected in parallel then the same current will flow through each component
• Adding a resistor in parallel reduces the total resistance
• If you have 2 resistors in parallel, their total resistance is less than the resistance of the smallest of the 2 resistors
• In parallel, both resistors have the same potential difference across them as the source
• The 'pushing force' making the current flow is the same as the source pd for each resistor you add
• By adding another loop, the current has more than 1 direction to go in. This increases the total current that can flow around the circuit
• Using V=IR, an increase in current means a decrease in the total resistance of the circuit