In parallel circuits, electrical components are connected alongside one another, forming extra loops.
An electron will not pass through every component on its way round the circuit. If one of the bulbs is broken then current will still be able to flow round the circuit through the other loop. If one bulb goes out, the other will stay on.
Since there are different loops, the current will split as it leaves the cell and pass through one or other of the loops An ammeter placed in different parts of the circuit will show how the current splits:
This is when:
Since energy has to be conserved, the energy transferred around the circuit by the electrons is the same whichever path the electrons follow.
The energy from the battery store is shared between the components depending on the resistance of each one.
Since potential difference is used to measure changes in energy, the potential difference supplied is equal to the potential differences across each of the parallel components but the value of current and resistance could be different.
The diagram shows a special case where both components have the same resistance and current and share the energy equally:
This is when:
It is possible to use a formula to work out the total resistance of two resistors in parallel.
This is the formula:
It can be rearranged into a more useful form:
1. What is the total resistance of a 6 Ω and a 3 Ω resistor connected in parallel?
2. What is the total resistance of two 10 Ω resistors connected in parallel?