Electric circuits - AQAParallel circuits

Electrical current transfers energy around circuits. There are two types of current: direct and alternating.

Part ofPhysics (Single Science)Electricity

Parallel circuits

In parallel circuits, electrical are connected alongside one another, forming extra loops.

Circuit rules

An will not pass through every component on its way round the circuit. If one of the bulbs is broken then will still be able to flow round the circuit through the other loop. If one bulb goes out, the other will stay on.

Current in parallel

Since there are different loops, the current will split as it leaves the cell and pass through one or other of the loops. An placed in different parts of the circuit will show how the current splits:

\(I_{1} = (I_{2}+I_{4}) = I_{3}\)

This is when:

  • current (I) is measured in amps (A)
I1 = I2 + I4 = I3

Potential difference in parallel

Since has to be conserved, the energy transferred around the circuit by the electrons is the same whichever path the electrons follow. Since is used to measure changes in energy, the potential difference supplied is equal to the potential differences across each of the parallel components:

\(V_{s} = V_{1} = V_{2}\)

This is when:

  • potential difference (V) is measured in volts (V)
Circuit containing a switch, 6V battery and two 100 ohm resistors in parallel. Label 1 points to a voltmeter connected across the battery, marked Vs. Labels 2 and 3 point to voltmeters connected across each resistor, marked V1 and V2 respectively.

Resistance in parallel

If are connected the supply current is divided between them. The overall is reduced as the current may follow multiple paths.