Circuits - AQA SynergySeries circuits

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

Part ofCombined ScienceMovement and interactions

Series circuits

In series circuits, electrical are connected one after another in a single loop.

Circuit rules

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

Learn more on series and parallel circuits in this podcast

Open Transcript

Current in series

A circuit is one loop; all electrons in that loop form one current. An will measure the same current wherever it is placed in the circuit:

\(\text I_{1} = \text I_{2} = \text I_{3} \)

This is when:

  • current (\(\text{I}\)) is measured in amps (A)
Circuit with a cell, two lamps and labels 1, 2 and 3 pointing at various points of the circuit.

Potential difference in series

The current will transfer from the power supply to the components in the circuit. Since energy has to be conserved, all of the source energy is shared between the components. Since is used to measure changes in energy, the potential difference supplied is equal to the total of the potential differences across all other components:

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

This is when:

  • potential difference \(\text{V}\) is measured in volts (V)
Circuit containing a switch, 6V battery and two 100 ohm resistors in series. 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 series

If are connected in a series circuit, the current must flow through both of them meaning the are added together to increase the total resistance of the circuit:

\(\text R_{total} = \text R_{1} + R_{2}\)

This is when:

  • resistance (\(\text{R}\)) is measured in ohms (Ω)

In series circuits:

  • current is the same through each component
  • the total potential difference of the power supply is shared between the components
  • the total resistance of the circuit is the sum of individual resistors

Example

What is the equivalent resistance of a 3 Ω resistor and a 2 Ω resistor in series?

\(\text R_{total} = \text R_{1} + R_{2}\)

\(\text R_{total} = 3 + 2\)

\(\text R_{total}\) = 5 Ω

Question

What is the equivalent resistance of a 10 Ω resistor and a 5 Ω resistor in series?

Next page
Parallel circuits
Previous page
Practical - factors that affect resistance

More guides on this topic

Related links