Potential Difference in Circuits (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award)) : Revision Note
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Potential difference in series circuits
Extended Tier Only
In a series circuit, the sum of potential differences across the components is equal to the total e.m.f. (electromotive force) of the power supply
Potential difference in a series circuit
In a series circuit the components share the e.m.f. of the power supply
Worked Example
In the circuit diagram below, the power source has an e.m.f., E, of 16 V. There is a potential difference of 10 V across component X. Calculate the potential difference across component Y.
Answer:
Step 1: Recall the rule for potential difference in series
The sum of potential differences across components in series is equal to the e.m.f. across the power source
Step 2: Write an equation to determine the potential difference across Y
E = VX + VY
Where:
E is the e.m.f. of the power source = 16 V
VX is the potential difference across X = 10 V
VY is the potential difference across Y
Recall that:
E = 16 V
VX = 10 V
Step 3: Substitute in the known quantities and calculate VY
16 = 10 + VY
Therefore, the potential difference across Y is 6 V
Potential difference in a parallel circuit
Extended Tier Only
The potential difference across each branch of a parallel circuit is the same as the e.m.f. of the power source
Potential difference in a parallel circuit
The power source has an e.m.f .of 12 V and there is a potential difference of 12 V across each branch
It is important to notice that the potential difference in a parallel circuit is equal across each branch
In the example above, if one branch in the circuit contained multiple components, the 12 V would be split between the components on that branch
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