diagram/labelLabel the quantities
Label current, potential difference and resistance on a circuit diagram, including the correct unit for each one.
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Example lesson history · Current, Potential Difference and Resistance in Simple Circuits
Identify circuit components · 26 Aug Measure current safely · 19 Aug Use units in calculations · 12 Aug2 September 2026
Current, Potential Difference and Resistance in Simple Circuits ✓ Teacher approved
This lesson focused on using the correct circuit language, placing meters in the right positions, and rearranging V = IR carefully. A useful check was the question “through or across?”: current is measured through a component, while potential difference is measured across it.
Work from this lesson
Your next steps
diagramDraw the meters correctly
Draw an ammeter in series and a voltmeter in parallel across a component. Check your diagram by tracing one unbroken loop.
calculationUse V = IR
Calculate the current when the potential difference is 12 V and the resistance is 4 ohms. Write the equation first, substitute values with units, then calculate and check the unit.
You learned the difference between current, potential difference and resistance. Current is the rate of flow of charge, measured in amperes with an ammeter in series. Potential difference is energy transferred per unit charge, measured in volts with a voltmeter in parallel. You also used V = IR to calculate current and saw that, for a fixed voltage, increasing resistance reduces current.
Current is the rate of flow of charge
Current tells you how much charge flows each second. It is measured in amperes (A). In a simple series circuit, the current is the same at every point in the loop.
Example If you trace one unbroken loop, the current is not split up in a single series circuit.
Common misconception Current gets used up as it passes through a component.
Check yourself Can you explain why the current stays the same in one series loop?
Potential difference is measured across a component
Potential difference is the energy transferred per unit charge between two points. It is measured in volts (V). A voltmeter must be connected in parallel across the component, not in series.
Example Use the question “through or across?”: current is measured through a component, potential difference is measured across it.
Common misconception A voltmeter should be connected in series.
Check yourself Can you point to where a voltmeter should go on a circuit diagram?
Rearrange V = IR to find current
When you know voltage and resistance, use I = V / R. Write the equation first, substitute the numbers with units, and then calculate. This avoids losing track of what each value means.
Example With V = 6 V and R = 3 Ω, I = 6 ÷ 3 = 2 A. If V stays at 6 V and R increases to 6 Ω, I becomes 1 A.
Common misconception You can calculate before writing the equation and checking the units.
Check yourself Can you rearrange V = IR and explain why a bigger resistance gives a smaller current when voltage stays fixed?
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Placing circuit metersIllustrative preview · not playable
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