# 4.3.2 Series & Parallel Circuits

### Series Circuits

• A series circuit consists of a string of two or more components, connected end to end:

Diagram showing two bulbs connected in series

• In a series circuit the current is the same at all points

The current is the same at all points in a series circuit

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### Potential Difference in Series

• When several cells are connected together in series, their combined EMF is equal to the sum of their individual EMFs

The total EMF of these cells is equal to the sum of their individual EMFs

• In a series circuit, the sum of potential differences across the components is equal to the total EMF of the power supply

In a series circuit the components share the EMF of the power supply

### Parallel Circuits

• A parallel circuit consists of two or more components attached along separate branches of the circuit

Diagram showing two bulbs connected in parallel

• The advantages of this kind of circuit are:
• The components can be individually controlled, using their own switches
• If one component stops working the others will continue to function
• In a parallel circuit, the current splits up – some of it going one way and the rest going the other
• This means that the current in each branch will be smaller than the current from the power supply

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### Determining Current in Parallel

• Because the current splits up, the sum of currents in each branch will equal the current from the power supply

In a parallel circuit, the current splits up, dividing between the various branches of the circuit

• Note that the current does not always split equally – often there will be more current in some branches than in others
• The current in each branch will only be identical if the components along each branch are identical (or at least have the same resistance)

### Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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