Pearson Edexcel GCSE Combined Science · P13

Electromagnetic induction

50 revision questions with answers for P13 Electromagnetic induction in Pearson Edexcel GCSE Combined Science (spec 1SC0). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below. Not official Pearson material.

All 50 questions and answers

Question 1 · Spec P13.2 · Higher only
What is electromagnetic induction in the situations studied?
Answer:
A changing magnetic field through a circuit produces a potential difference.
Question 2 · Spec P13.2 · Higher only
How can moving a magnet relative to a coil induce a voltage?
Answer:
Movement changes the magnetic field linking the coil.
Question 3 · Spec P13.2 · Higher only
Why does a stationary magnet usually give no induced voltage in a stationary coil?
Answer:
The magnetic field linking the coil is not changing.
Question 4 · Spec P13.2 · Higher only
How does faster relative motion affect induced potential difference?
Answer:
It increases the field's rate of change, usually increasing the induced voltage.
Question 5 · Spec P13.2 · Higher only
How can a stronger magnet affect induced voltage for the same motion?
Answer:
It generally increases the voltage because the field change is greater.
Question 6 · Spec P13.2 · Higher only
How can more coil turns affect the induced voltage?
Answer:
More turns experience the changing field, increasing the total induced voltage.
Question 7 · Spec P13.2 · Higher only
What happens to induced voltage if the magnet's motion reverses?
Answer:
Its polarity reverses, with other conditions unchanged.
Question 8 · Spec P13.2 · Higher only
What happens if the approaching magnet's pole is reversed?
Answer:
The induced voltage polarity reverses.
Question 9 · Spec P13.2 · Higher only
What happens if both the moving direction and magnet pole reverse?
Answer:
The induced polarity stays the same as before, for otherwise comparable motion.
Question 10 · Spec P13.2 · Higher only
How does the induced current's magnetic field relate to the original change?
Answer:
It opposes the change that produced it.
Question 11 · Spec P13.2 · Higher only
A north pole approaches a conducting coil. What effect does the induced field have?
Answer:
It opposes the approach; the near coil end acts as a north pole.
Question 12 · Spec P13.2 · Higher only
A north pole is withdrawn from a conducting coil. What effect does the induced field have?
Answer:
It opposes withdrawal; the near coil end acts as a south pole.
Question 13 · Spec P13.2 · Higher only
Does the induced field always oppose the original magnetic field?
Answer:
No. It opposes the change, so it can reinforce a decreasing field or oppose an increasing one.
Question 14 · Spec P13.2 · Higher only
When can an induced potential difference produce a sustained current while the field changes?
Answer:
When the conducting circuit is closed.
Question 15 · Spec P13.5 · Higher only
What does the primary coil do in a transformer?
Answer:
Its alternating current creates a changing magnetic field.
Question 16 · Spec P13.5 · Higher only
How does the secondary coil receive energy without a direct electrical connection?
Answer:
The changing magnetic field links it and induces an alternating potential difference, driving current in a closed secondary circuit.
Question 17 · Spec P13.5 · Higher only
Why is alternating current suitable for transformer operation?
Answer:
It continually changes the magnetic field linking the coils.
Question 18 · Spec P13.5 · Higher only
Why does steady direct current not maintain a transformer output?
Answer:
After the initial change, its magnetic field is steady, so no continuing secondary voltage is induced.
Question 19 · Spec P13.5 · Higher only
How does a shared magnetic core help the transformer?
Answer:
It guides the changing magnetic field so it links both circuits effectively.
Question 20 · Spec P13.6 · Higher only
What type of voltage can a transformer change continuously?
Answer:
An alternating voltage.
Question 21 · Spec P13.9
What does a step-up transformer do in the National Grid?
Answer:
It raises the voltage for transmission from the power station.
Question 22 · Spec P13.9
What does a step-down transformer do in the National Grid?
Answer:
It lowers voltage nearer consumers to suitable distribution or domestic levels.
Question 23 · Spec P13.9
Why is a step-up transformer placed before long transmission lines?
Answer:
High voltage allows a lower current for a given transmitted power.
Question 24 · Spec P13.9
Why reduce voltage before supplying homes?
Answer:
Transmission voltages are unsuitable and hazardous for ordinary domestic appliances.
Question 25 · Spec P13.8
Why does high transmission voltage reduce energy losses?
Answer:
For a fixed power it lowers current, reducing resistive heating in the lines.
Question 26 · Spec P13.8
Which equation explains lower current at higher voltage for the same power?
Answer:
P = VI, so I = P/V.
Question 27 · Spec P13.8
Which equation links cable heating power to current?
Answer:
P_loss = I²R.
Question 28 · Spec P13.8
At fixed transmitted power, what happens to current if voltage doubles?
Answer:
Current halves.
Question 29 · Spec P13.8
If cable current halves at fixed resistance, what happens to heating power?
Answer:
It becomes one-quarter, because loss is proportional to current squared.
Question 30 · Spec P13.8
Why does reducing line loss improve transmission efficiency?
Answer:
A greater fraction of the supplied energy reaches consumers usefully.
Question 31 · Spec P13.8
Find current when 100,000 W is transmitted at 10,000 V.
Answer:
I = P/V = 100,000/10,000 = 10 A.
Question 32 · Spec P13.8
Find cable heating power for 10 A through 2 Ω.
Answer:
P_loss = 10² × 2 = 200 W.
Question 33 · Spec P13.8
The same 100,000 W is sent at 1,000 V. Find current.
Answer:
I = 100,000/1,000 = 100 A.
Question 34 · Spec P13.8
For 100 A through the same 2 Ω cable, find heating power.
Answer:
100² × 2 = 20,000 W, much greater than at 10 A.
Question 35 · Spec P13.8
Why is comparing transmission at the same supplied power important?
Answer:
Otherwise changes in power demand could confuse the effect of voltage on current and losses.
Question 36 · Spec P13.10
State the ideal-transformer power equation.
Answer:
VpIp = VsIs: primary input power equals secondary output power for 100% efficiency.
Question 37 · Spec P13.10
Does an ideal transformer create extra energy when it raises voltage?
Answer:
No. Output current decreases so output power equals input power.
Question 38 · Spec P13.10
A primary uses 230 V and 2 A. Find ideal secondary power.
Answer:
230 × 2 = 460 W.
Question 39 · Spec P13.10
An ideal transformer supplies 460 W at 46 V. Find secondary current.
Answer:
Is = 460/46 = 10 A.
Question 40 · Spec P13.10
A secondary provides 12 V at 5 A. Find ideal input power.
Answer:
12 × 5 = 60 W.
Question 41 · Spec P13.10
An ideal transformer outputs 60 W with 240 V primary voltage. Find primary current.
Answer:
Ip = 60/240 = 0.25 A.
Question 42 · Spec P13.10
A primary takes 120 V at 0.50 A and the secondary current is 3 A. Find secondary voltage.
Answer:
Vs = (120 × 0.50)/3 = 20 V.
Question 43 · Spec P13.10
An ideal secondary supplies 400 V at 0.20 A. If primary current is 2 A, find primary voltage.
Answer:
Vp = (400 × 0.20)/2 = 40 V.
Question 44 · Spec P13.10
For an ideal transformer, voltage rises by factor five. How does current change?
Answer:
Secondary current is one-fifth of primary current, preserving power.
Question 45 · Spec P13.10
For an ideal transformer, voltage falls by factor four. How does current change?
Answer:
Secondary current is four times primary current.
Question 46 · Spec P13.10
An ideal transformer has 500 W input and 250 V output. Find output current.
Answer:
500/250 = 2.0 A.
Question 47 · Spec P13.10
Why can real output power be lower than VpIp?
Answer:
Some input energy is dissipated, so a real transformer can be less than 100% efficient.
Question 48 · Spec P13.8
A transmission system supplies 50 kW and loses 2 kW. Find energy-transfer efficiency.
Answer:
Useful power = 48 kW; efficiency = 48/50 = 96%.
Question 49 · Spec P13.9
Why are several voltage-changing stages used rather than one voltage everywhere?
Answer:
High voltage suits efficient long-distance transfer, while lower voltages suit local distribution and safe practical use.
Question 50 · Spec P13.8
What should a Grid design evaluation compare?
Answer:
Transmission losses, voltage suitability, infrastructure cost and reliability, using the provided evidence.

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