Electrical charge and current — AQA GCSE Physics
Test yourself on Electrical charge and current with AQA GCSE practice questions.
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Electrical charge and current explained
Charge does not flow on its own; something has to push it.
Read the full explanation
That push is a potential difference, supplied by a cell, a battery or a mains supply. A cell or battery transfers energy from its chemical store to the charges and drives them round the circuit. Two conditions must both hold for charge to flow. There must be a source of potential difference, and the circuit must be complete, forming a closed loop of conductors with no gaps. Open a switch, blow a fuse or break a wire in a series circuit and the current everywhere stops instantly. However, in a parallel circuit, a break in one branch does not stop current flowing in other intact branches. Adding more cells in series raises the potential difference, so the current increases; closing a switch that adds a parallel branch lowers the total resistance, so the current from the supply increases.
Your focus
- State the two conditions needed for charge to flow round a circuit.
- Explain why opening a switch stops the current everywhere in a single loop.
- Predict the effect on the current of adding an extra cell in series with the supply.
Show all 4 objectives
- Explain why closing a switch that adds a parallel branch increases the current from the battery.
Electrical charge and current exam tips
Marking Points
- one mark for stating that a source of potential difference is needed to make charge flow
- one mark for stating that the circuit must be closed or complete
- one mark for explaining that an open switch or break stops the current throughout a series circuit
- one mark for linking a change in supply potential difference or total resistance to a change in current
Examiner Tips
- 💡Name both conditions, the source and the complete circuit, because a one-condition answer only scores half.
- 💡Use the phrase charge flows rather than electricity flows, which is too vague to credit.
- 💡When a switch is closed or opened, check if it is in a series loop or a parallel branch before deciding if the whole current stops.
Common Mistakes
- saying the battery supplies the charges, when the charges are already in the wires and the battery supplies the potential difference
- claiming current is used up as it goes round the circuit
- thinking a break in a series circuit only stops the current after the break, rather than everywhere instantly
- assuming a break in one branch of a parallel circuit stops the current in all other branches