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 pass 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. If one loop has less resistance than the other, there will be more current in the loop with the lower resistance. An ammeter placed in different parts of the circuit will show how the current splits:
This is when:
current (I) is measured in amps (A)
If the resistance of any component in a parallel circuit changes, this will change the value of the current in that loop and the total current supplied by the battery. It does not affect the current in the other loop.
Since energy has to be conserved, the energy transferred around the circuit by the electrons is the same whichever path the electrons follow. 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:
This is when:
potential difference (V) is measured in volts (V)
If the resistance of any component in a parallel circuit changes, this will have no effect on the potential difference across any of the components.