Electromagnetic Induction | Edexcel GCSE Physics, Higher tier (1PH0)
Electromagnetic Induction
- 81 questions
- 8 subtopics
- Paper 2
- Paper 2
Electromagnetic Induction is examined in Paper 2, Physics 2.
It covers inducing a current by moving a magnet, factors affecting an induced potential difference, alternators and microphones, how a transformer works, the transformer turns-ratio equation, the national grid, and step-up and step-down transformers, transformer power calculations and why high-voltage transmission reduces energy loss.
Sample questions from Electromagnetic Induction
Answer each one closed book first, then open the answer.
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Inducing a current by moving a magnet
Explain why a current flows in a coil only while a magnet is being moved into it.
Show the answer
A potential difference is induced only while the magnetic field passing through the coil is changing. -
Factors affecting an induced potential difference
Describe how the direction of the induced current changes when a magnet is pulled out of a coil instead of pushed into it.
Show the answer
The induced current flows in the opposite direction. -
Alternators and microphones
Describe how the output of a dynamo changes during one complete rotation of its coil.
Show the answer
It rises to a peak and falls to zero twice, but it never reverses direction. -
How a transformer works
Explain why the two coils of a transformer can be electrically insulated from each other and still transfer energy.
Show the answer
The energy is carried between them by the changing magnetic field, not by charge flowing from one coil to the other. -
The transformer turns-ratio equation
A transformer changes 230 V into 11.5 V and has 2000 turns on its primary coil. Calculate the number of turns on its secondary coil.
Show the answer
Secondary turns = 2000 × 11.5 ÷ 230 = 100 turns. -
The national grid, and step-up and step-down transformers
State the effect of transferring electrical energy at high voltage on the efficiency of the transmission network.
Show the answer
The efficiency is higher, because less of the energy is wasted heating the cables. -
Transformer power calculations
A transformer takes 2.0 A from a 230 V supply and gives an output of 23 V. Calculate the output current.
Show the answer
Input power = 230 × 2.0 = 460 W, so output current = 460 ÷ 23 = 20 A. -
Why high-voltage transmission reduces energy loss
Explain why raising the transmission voltage ten times reduces the power wasted in the cables one hundred times.
Show the answer
The current falls to a tenth for the same power, and the wasted power depends on the square of the current.
The 8 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Inducing a current by moving a magnet | Producing a potential difference with a bar magnet and a coil, why only a changing field induces one, moving the coil instead, and wind turbines, power stations and dynamos. | 8 |
| Factors affecting an induced potential difference | The speed, magnet strength and number of turns that set the induced potential difference, reversing the movement or the pole, and why the induced field opposes the change that made it. | 8 |
| Alternators and microphones | How alternators and dynamos produce alternating and direct current with slip rings or a commutator, their outputs over one rotation, increasing a generator's output, and how microphones, loudspeakers and headphones convert between sound and electrical signals. | 16 |
| How a transformer works | The construction of a transformer, how an alternating current in the primary coil induces a potential difference in the secondary, why direct current gives no output, the soft iron core, and step-up and step-down transformers and their turns. | 12 |
| The transformer turns-ratio equation | The turns ratio equation, calculating an output voltage or the number of turns on a coil, and telling a step-up from a step-down transformer by its turns. | 8 |
| The national grid, and step-up and step-down transformers | Transmitting electrical energy at high voltage and low current to cut heating losses in cables, the national grid and its thick cables, where and why step-up and step-down transformers are used, the 230 V mains, and why the grid uses alternating current. | 13 |
| Transformer power calculations | The power equation for a 100% efficient transformer, calculating an output current, an output voltage or a primary current, and why stepping the voltage up lowers the current. | 8 |
| Why high-voltage transmission reduces energy loss | The equations for power and for power wasted in a cable, why a tenfold voltage rise cuts losses a hundredfold, and calculations of current and wasted power in transmission cables. | 8 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
Edexcel GCSE Physics, Higher tier Active Recall Guide
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