Why does a bulb get dimmer when you add another one in a line? Why does one broken bulb in a house not switch off all the others? Electricity questions look like a lot of separate facts, but a handful of ideas (current, potential difference, resistance and the way circuits are joined) explain almost all of them.
This free quiz starts with current and charge, then potential difference and resistance, then series and parallel circuits, the graphs of different components, power and energy, and the mains supply. Wherever a calculation can be checked automatically, a script recalculates the answer. Every answer comes with a short explanation, and the one question that needs a Higher tier idea is flagged so that Foundation students can leave it out.
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A 9 V cell is connected in series with a 10 Ω resistor and a 20 Ω resistor. What is the potential difference across the 20 Ω resistor?
Answer: C, 6 V
The total resistance is 30 Ω, so the current is 9 V ÷ 30 Ω = 0.3 A. The potential difference across the 20 Ω resistor is 0.3 A × 20 Ω = 6 V. Check: 3 V + 6 V = 9 V.
A current of 3 A flows through a heating element of resistance 5 Ω. What is the power transferred in the element?
Answer: A, 45 W
Power = current² × resistance = 3² × 5 = 9 × 5 = 45 W.
Current is the rate of flow of charge: the charge that passes a point each second, in amperes. Charge only flows round a complete loop that includes a source of potential difference. The potential difference (also called voltage) is the energy transferred to each coulomb of charge, in volts, and the resistance of a component, in ohms, tells you how much it opposes the flow.
The three are linked by potential difference = current × resistance. For a fixed resistance, doubling the potential difference doubles the current. A good habit is to write the equation, rearrange it for the quantity you want, then substitute with the right units.
In a series circuit there is one loop. The current is the same everywhere, the potential difference of the supply is shared between the components and the total resistance is the sum of the resistances, so adding a component makes the current smaller.
In a parallel circuit each branch is connected across the same two points. The potential difference is the same across every branch, the current from the supply is the sum of the currents in the branches, and each branch works independently of the others. You should be able to explain why adding a branch gives the charge more routes, so the total resistance of the circuit goes down. AQA says students do not have to calculate the total resistance of two parallel resistors, and this quiz does not ask for it.
At a constant temperature a resistor has a constant resistance, so its graph of current against potential difference is a straight line through the origin. The filament of a lamp gets hot as the current grows, its resistance rises, and the graph bends over. A diode conducts in one direction only and has a very high resistance the other way. A thermistor's resistance falls as it warms up and an LDR's resistance falls as the light gets brighter.
Power is the energy transferred each second, in watts. For a device it can be found from potential difference × current, or from current² × resistance, and the energy transferred over a time is power × time (with the time in seconds). Energy can also be found from charge × potential difference. Because the heating in a wire grows with the square of the current, a cable that carries a large current is made thick, with a low resistance.
The mains supply in the UK is alternating, at about 230 V and 50 Hz. A mains plug has a live wire that brings the supply, a neutral wire that completes the circuit and an earth wire that is a safety wire and carries a current only if there is a fault. Equation sheets: for the 2027 papers AQA, Pearson Edexcel and OCR each say that a physics equation sheet comes with the papers, so the skills that matter are choosing the right equation, rearranging it and converting units. The explanation of every calculation in this quiz shows the equation it uses, and you should check which sheet your own board gives you.
It is written to fit all three: current, potential difference, resistance, series and parallel circuits, the graphs of resistors, lamps and diodes, and the power and energy equations appear in the GCSE Physics specifications of AQA, Pearson Edexcel and OCR. We have not checked the Combined Science specifications for this quiz, so check yours. The boards word things differently and a few details vary, so look at your own board's specification for the exact content of your course.
Not in this quiz. AQA's specification says students are not required to calculate the total resistance of two resistors joined in parallel, and Edexcel asks for a calculation only for series circuits and an explanation for parallel ones. OCR's wording is less clear: one point asks for a qualitative explanation only and another mentions calculations in series and parallel circuits. The parallel questions here use the facts that the potential difference is the same across every branch and that the branch currents add up, so ask your teacher or check your board's specification if you sit OCR.
Only one: the question about why a thick, low resistance cable wastes less energy. Edexcel prints it as Higher tier content, so we flag it, even though it can be answered from the power equations that every student uses. If you choose Foundation, the quiz leaves it out. If you choose Higher, you get everything. The other electricity content in this quiz is not marked as Higher tier in the three specifications we read.
No. Each attempt picks a set of questions from a larger bank and shuffles the order of the answers, so you cannot learn them by position. Your answers and score stay on your own device, in your browser, so you can carry on after a reload; you can clear them at any time with the "Clear my saved progress" button. We only count anonymous, cookie-free visits and whether a quiz was finished, never your answers or who you are.
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These practice questions were written by Cloudia Tutoring. They are not official AQA, Pearson Edexcel or OCR material, and Cloudia Tutoring is not affiliated with or endorsed by any exam board or the Department for Education. Always check your own exam board's specification.
Reviewed by Claudia Edwards on 20 October 2026 Last updated .
