Physics · Unit 17
Electricity and Electromagnetism
Charges, circuits and fields
This unit joins the two subjects that were separated in the earlier one, and the joining is done by fields - a way of describing influence spread through space rather than acting at a point.
It covers voltage, current and resistance, series and parallel circuits, electrical power and energy, magnetic fields, and electromagnetic induction, which is how essentially all electricity is generated.
This unit breaks down into 20 short steps and 120 questions, starting at difficulty 2 and building to 3. Below you can see exactly what it covers, how the path is structured, and worked examples with explanations.
- Steps
- 20
- Questions
- 120
- Difficulty
- 2-3
What this unit covers
- Voltage, Current, Resistance
- Electrical Power and Energy
- Magnetic Fields
- Electromagnetic Induction
- Series and Parallel Circuits
Where this fits
Needs Electricity and Magnets. Leads into Modern Physics.
Where people slip
In parallel, adding a branch lowers the total resistance. It feels backwards and it is the point at which circuit reasoning most often fails.
How the unit is structured
Electricity and Electromagnetism runs as 20 short steps that unlock in order. 15 are practice rounds and 5 are challenge rounds that pull together everything before them. Questions start at difficulty 2 and climb to 3 as you progress.
Challenge rounds
Example questions
30 real questions from this unit, with the answer and the reason behind it, grouped by what they practise. There are 120 in the unit altogether.
Electrical Power and Energy
- Fill the blankLevel 2
1. Home electricity bills usually measure energy used in kilowatt-____.
- hourscorrect
- seconds
- amps
- volts
A kilowatt-hour is the energy used by a 1 kW device in one hour - the unit shown on electricity bills.
- Guess the numberLevel 2
2. An appliance runs at 230 V and draws 2 A. What is its power? (P = V x I)
Answer: 460 W
Electrical power P = V x I = 230 x 2 = 460 W.
- Match the pairsLevel 2
3. Match each quantity to its unit.
Answer: Power = Watt; Energy = Joule; Time = Second; Charge = Coulomb
Power is measured in watts, energy in joules, time in seconds, and charge in coulombs.
- Multiple choiceLevel 2
4. Which equation gives the electrical power used by a device?
- P = V x Icorrect
- P = V / I
- P = I / V
- P = V - I
Electrical power equals voltage times current: P = V x I.
- Choose all that applyLevel 3
5. Which of these equations correctly give the power dissipated in a resistor? (Select all that apply.)
- P = VIcorrect
- P = I squared Rcorrect
- P = V squared / Rcorrect
- P = V / I
P = VI, P = I^2 R and P = V^2 / R are all equivalent forms; the others are not valid power equations.
- Fact or fibLevel 3
6. For a resistor on an AC supply, the average power dissipated equals Vrms multiplied by Irms.
Answer: True
Using rms values, the average AC power for a pure resistor is P = Vrms x Irms, just like DC power.
Electromagnetic Induction
- Build the sentenceLevel 2
7. Build a true sentence about electromagnetic induction.
Answer: A changing magnetic field induces a voltage
Induction happens only when the magnetic field through a coil changes, which induces a voltage.
- Fill the blankLevel 2
8. An electric ____ turns electrical energy into movement, while a generator does the reverse.
- motorcorrect
- generator
- resistor
- fuse
A motor uses current in a magnetic field to produce motion; a generator uses motion to produce current.
- Match the pairsLevel 2
9. Match each device to what it does.
Answer: Electric motor = Electrical energy to motion; Generator = Motion to electrical energy; Transformer = Changes AC voltage; Battery = Chemical energy to electrical
A motor turns electricity into motion, a generator turns motion into electricity, a transformer changes AC voltage, and a battery turns chemical energy into electrical energy.
- Choose all that applyLevel 3
10. Which changes would INCREASE the EMF induced when a magnet is pushed into a coil?
- Moving the magnet fastercorrect
- Using a stronger magnetcorrect
- Adding more turns to the coilcorrect
- Holding the magnet still inside the coil
A faster movement, a stronger magnet, and more turns all raise the rate of change of flux linkage; holding the magnet still induces no EMF.
- Fact or fibLevel 3
11. By Lenz's law, an induced current always flows in the direction that opposes the change producing it.
Answer: True
Lenz's law is a consequence of energy conservation: the induced current opposes the change in flux causing it.
- Guess the numberLevel 3
12. A coil of 200 turns experiences a change in magnetic flux of 0.010 Wb in 0.50 s. Using EMF = N x (change in flux / time), what is the magnitude of the induced EMF?
Answer: 4 V
EMF = N dPhi/dt = 200 x (0.010 / 0.50) = 200 x 0.020 = 4.0 V.
Magnetic Fields
- Fact or fibLevel 2
13. Cutting a bar magnet in half gives two magnets, each with its own north and south pole.
Answer: True
True - you can never isolate a single pole; each piece becomes a complete magnet with two poles.
- Fill the blankLevel 2
14. Two north poles pushed towards each other will ____ each other.
- repelcorrect
- attract
- stick to
- melt
Like poles repel, so two north poles push apart; only opposite poles attract.
- Match the pairsLevel 2
15. Match each magnetism term to its meaning.
Answer: Two ends of a magnet = Poles; Coil of wire carrying current = Solenoid; Adding an iron core = Stronger field; Region where the force acts = Magnetic field
Poles are the ends of a magnet, a solenoid is a current-carrying coil, an iron core strengthens the field, and the field is the region where the force acts.
- Multiple choiceLevel 2
16. What shape is the magnetic field around a straight current-carrying wire?
- Circles around the wirecorrect
- Straight lines along the wire
- A single dot at the centre
- There is no field
A current in a straight wire produces concentric circular field lines wrapping around the wire.
- Odd one outLevel 2
17. Which of these metals is NOT magnetic?
- Coppercorrect
- Iron
- Nickel
- Cobalt
Copper is not attracted by a magnet, while iron, nickel and cobalt are all magnetic.
- Guess the numberLevel 3
18. A wire 0.20 m long carrying 5.0 A lies at right angles to a magnetic field of flux density 0.40 T. Using F = B I L, what is the force on it?
Answer: 0.4 N
F = B I L = 0.40 x 5.0 x 0.20 = 0.40 N.
Series and Parallel Circuits
- Build the sentenceLevel 2
19. Build a true sentence about a series circuit.
Answer: Series bulbs share the battery voltage
In series the single supply voltage is divided, so the bulbs share the battery voltage between them.
- Choose all that applyLevel 2
20. Which statements are true of a parallel circuit? Select all that apply.
- Each branch receives the full supply voltagecorrect
- There is more than one path for the currentcorrect
- The total current is shared between the branchescorrect
- If one branch breaks, current stops in all branches
Parallel branches each get the full supply voltage and offer separate paths, and the total current is shared, so one broken branch does not stop the others.
- Fact or fibLevel 2
21. In a simple series circuit, if one bulb breaks the others also go out.
Answer: True
True - a series circuit is a single loop, so a break anywhere stops the current everywhere.
- Fill the blankLevel 2
22. Adding more bulbs in ____ makes each bulb dimmer because they share the supply voltage.
- seriescorrect
- parallel
- isolation
- reverse
In series the fixed supply voltage is divided among more components, so each bulb gets less and glows dimmer.
- Guess the numberLevel 2
23. A 5 ohm resistor and a 10 ohm resistor are joined in series. What is their total resistance?
Answer: 15 ohms
Resistances in series simply add: 5 + 10 = 15 ohms.
- Multiple choiceLevel 3
24. What does Kirchhoff's first law (the current law) state?
- The total current into a junction equals the total current out of itcorrect
- The voltage is the same across every component
- Current always increases at a junction
- Resistances in series add together
Charge is conserved, so the total current flowing into a junction equals the total current flowing out of it.
Voltage, Current, Resistance
- Fill the blankLevel 2
25. In the equation V = I x R, the letter I stands for the electric ____.
- currentcorrect
- voltage
- resistance
- power
I represents current, measured in amperes; V is voltage and R is resistance.
- Guess the numberLevel 2
26. A 3 A current flows through a 4 ohm resistor. What is the voltage across it? (V = I x R)
Answer: 12 V
By Ohm's law V = I x R = 3 x 4 = 12 V.
- Match the pairsLevel 2
27. Match each electrical quantity to its unit.
Answer: Voltage = Volt; Current = Ampere; Resistance = Ohm; Charge = Coulomb
Voltage is measured in volts, current in amperes, resistance in ohms, and charge in coulombs.
- Multiple choiceLevel 2
28. How must an ammeter be connected to measure the current through a bulb?
- In series with the bulbcorrect
- In parallel with the bulb
- Across the battery only
- It does not need connecting
An ammeter is connected in series so the same current passing through the bulb flows through it.
- Choose all that applyLevel 3
29. Which of these changes would INCREASE the resistance of a metal wire?
- Increasing its lengthcorrect
- Reducing its cross-sectional areacorrect
- Raising its temperaturecorrect
- Making the wire thicker
Resistance rises with greater length, smaller cross-sectional area, and higher temperature; a thicker wire lowers resistance.
- Sort into groupsLevel 3
30. Sort each component by whether it obeys Ohm's law (ohmic) or not (non-ohmic).
Answer: Metal wire at constant temperature = Ohmic; Fixed resistor = Ohmic; Filament lamp = Non-ohmic; Semiconductor diode = Non-ohmic
Ohmic components keep a constant resistance and a straight I-V line; filament lamps and diodes do not.
Where these questions come from. Each unit starts as a plan of the concepts it should cover and the difficulty it should span. Questions are written against that plan with AI assistance, then checked by a validator that rejects anything without a single defensible answer, an explanation, or plausible wrong options. How we write questions sets out the whole process, and corrections are fixed in the bank and reach the site and the app the same day.
How you practise
This unit mixes 15 different question formats, so you are recalling and applying rather than recognising the same layout every time.
- Build the sentence
- Choose all that apply
- Fact or fib
- Fill the blank
- Guess the number
- Match the pairs
- Multiple choice
- Odd one out
- Picture question
- Put in order
- Sort into groups
- Spell it
- Tap the pairs
- True or false
- Type the answer
Practise Electricity and Electromagnetism
120 questions across 20 steps. Start with step one and crawl at your own pace.
Play this unitRead about Electricity and Electromagnetism
Explainers from our blog on what this unit covers. Each one ends with real questions from the bank.
- Ohm's Law: How Voltage, Current, and Resistance ConnectOhm's law links voltage, current, and resistance in simple circuits. Learn the formula, rearrange it safely, and understand when the model applies.August 14, 2026 · 6 min read
- How a Simple Electric Circuit WorksA circuit needs a source, a complete path and components that use electrical energy. Once you can follow the loop, circuit diagrams become much less mysterious.July 24, 2026 · 5 min read
- How Electromagnetic Induction Generates CurrentA changing magnetic field can create a potential difference in a conductor. This principle, called electromagnetic induction, is the basis of generators and many other electrical devices.August 8, 2026 · 5 min read
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