Potential Difference in Circuits (Cambridge International IGCSE Science)

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 = V_X* *+ V_Y

• Where:

  • E is the e.m.f. of the power source = 16 V
  • V_X is the potential difference across X = 10 V
  • V_Y is the potential difference across Y

• Recall that:

  • E = 16 V
  • V_X = 10 V

Step 3: Substitute in the known quantities and calculate V_Y

16 = 10 + V_Y

• Therefore, the potential difference across Y is 6 V

Potential difference in parallel circuits

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