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electromagnets

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4 detailed 50-minute lessons with teaching scripts, worked examples, parent guides, and assessment criteria.

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Lesson Overview

Total Lessons: 4
Tier: Foundation and Higher
Duration: 50 minutes per lesson (200 minutes total)
Exam Boards: AQA, Edexcel, OCR, Eduqas, CCEA

Learning Objectives

Prerequisites

Materials & Equipment

Lesson 1: Introduction: electromagnets

Duration: 50 minutes

Starter Activity (5 minutes)

Quick Recall

Write down everything you already know about electromagnets. Then check against the key terms: Electromagnet, Solenoid, Motor effect. Use a mini-whiteboard or paper.

Main Content (35 minutes)

Parent/Teacher Guide:
Before lesson: Read the script below. Pre-teach key vocab: Electromagnet, Solenoid, Motor effect.
If stuck: Re-read the revision notes (link above), then break the content into smaller steps.
Extension: See the Stretch & Challenge ideas in Lesson 4.
Teaching Script (35 mins):
Mins 0-5 - Hook: "Today: electromagnets. By the end you will be able to answer exam questions on it unaided. It connects to the rest of Physics because the ideas here recur across the spec."
Mins 5-20 - Direct Instruction: Work through the core ideas below one at a time; after each, ask your student to explain it back in their own words.
Mins 20-30 - Guided Practice: Model the worked example together, then let your student attempt the first practice question with guidance.
Mins 30-35 - Independent Practice: 2-3 practice questions from Lesson 3 below, with immediate feedback.
First Look

Start with the revision notes summary, then attempt: Foundation State three ways to increase the strength of an electromagnet.

Plenary (5 minutes)

Check Out

Your student states one thing they learned and one question they still have about electromagnets.

Lesson 2: Core Concepts: electromagnets

Duration: 50 minutes

Starter Activity (5 minutes)

Review Previous Lesson

Quick recap: write 3 key points from Lesson 1 on electromagnets. Check them against the notes below.

Main Content (35 minutes)

Electromagnet: A coil of wire (solenoid) with a current flowing through it, which produces a magnetic field. Unlike a permanent magnet, an electromagnet can be switched on and off by turning the current on and off.
Solenoid: A coil of wire that produces a strong, uniform magnetic field inside it when a current flows. The field inside is strong and parallel to the axis; the field outside is similar to a bar magnet.
Motor effect: When a current-carrying wire is placed in a magnetic field, the wire experiences a force. This is the motor effect. The force is greatest when the wire is perpendicular to the magnetic field.
Fleming's left-hand rule: A rule to determine the direction of the force on a current-carrying wire in a magnetic field. First finger = direction of magnetic field (N to S), Second finger = direction of current, Thumb = direction of force (motion).
Why an iron core helps: The iron becomes an induced magnet when the current flows, adding its own magnetic field to the solenoid's field. This makes the combined field much stronger. Soft iron is used because it loses its magnetism when the current is switched off, allowing the electromagnet to be turned off quickly.
Fleming's Left-Hand Rule: Hold your left hand with your first finger, second finger and thumb at right angles to each other: • First finger = direction of the magnetic Field (N to S) • Second finger = direction of the Current (conventional current, + to -) • Thumb = direction of the Force (motion) Remember: F irst = F ield, se C ond = C urrent, thu M b = M otion
ItemDetail
Increasing the currentStronger magnetic field
Adding more turns to the coilStronger magnetic field
Adding an iron core inside the solenoidMuch stronger magnetic field (iron becomes an induced magnet)
Using a soft iron core (rather than steel)Easier to switch off — soft iron loses magnetism quickly when current stops

Practice (10 minutes)

Q: Foundation State three ways to increase the strength of an electromagnet.

Answer: Q1: Three from: increase the current, add more turns of wire to the coil, add a soft iron core inside the coil, use a higher voltage power supply to increase current.

Plenary (5 minutes)

Explain Back

Your student teaches the key points back to you without looking. Fill any gaps immediately.

Lesson 3: Application: electromagnets

Duration: 50 minutes

Starter Activity (5 minutes)

Quick Recall

Recall the key terms: Electromagnet, Solenoid, Motor effect. Define each in one sentence.

Main Content (35 minutes)

Parent/Teacher Guide: Let your student attempt each question alone first, then compare with the model answer. Award method marks for correct working even if the final answer is wrong.

Q1: Foundation State three ways to increase the strength of an electromagnet.

Answer: Q1: Three from: increase the current, add more turns of wire to the coil, add a soft iron core inside the coil, use a higher voltage power supply to increase current.

Q2: Foundation Explain why an electromagnet is more useful than a permanent magnet in a scrap yard crane.

Answer: Q2: An electromagnet can be switched on and off by controlling the current. In a scrap yard, this allows the crane to pick up metal objects when the current is on and release them when the current is switched off. A permanent magnet cannot be switched off, so it could not release the objects.

Q3: Higher A wire of length 0.1 m carries a current of 2 A perpendicular to a magnetic field of 0.5 T. Calculate the force on the wire.

Answer: Q3: F = B × I × L = 0.5 × 2 × 0.1 = 0.1 N

Q4: Higher Explain how a split ring commutator keeps a DC motor spinning in the same direction.

Answer: Q4: The split ring commutator reverses the direction of current in the coil every half turn. Without it, the coil would rotate half a turn, then the forces would reverse and push it back. The commutator swaps the connections to the coil at the right moment, ensuring the force on each side of the coil continues to push in the same rotational direction so the motor keeps spinning.

Q5: Foundation Describe how a loudspeaker converts an electrical signal into sound waves.

Answer: Q5: A coil attached to the speaker cone sits in a permanent magnetic field. An alternating current flows through the coil. As the current changes direction, the force on the coil changes direction (motor effect). This makes the coil and cone vibrate back and forth. The vibrating cone produces sound waves that match the frequency of the alternating current.

Plenary (5 minutes)

Error Review

Review any questions answered incorrectly. Identify whether the error was knowledge, method, or reading the question.

Lesson 4: Exam Practice: electromagnets

Duration: 50 minutes

Starter Activity (5 minutes)

Command Words

Review what these command words require: state (one point), describe (say what happens), explain (say why), compare (both sides), evaluate (judgement).

Main Content (35 minutes)

Extended Answer

Extended question: Extended Answer 6 marks: Explain how the motor effect causes a current-carrying coil to rotate in a magnetic field. Explain the role of the split ring commutator in keeping the motor turning. <div class="

A coil of wire carrying current sits in a magnetic field between two permanent magnets. The current flows in opposite directions on each side of the coil. Using Fleming's left-hand rule, the side of the coil where current flows upwards experiences a downward force, while the side where current flows downwards experiences an upward force. These two forces act in opposite directions on opposite sides of the coil, creating a turning effect (torque) that makes the coil rotate. However, after half a turn, the sides of the coil have swapped positions. Without the commutator, the current would still flow in the same direction in each side, so the forces would now push in the wrong direction and the coil would stop or reverse. The split ring commutator reverses the direction of current in the coil every half turn, just as the coil passes the vertical position. This means the force on each side of the coil always pushes in the same rotational direction, keeping the motor spinning continuously. Mark scheme: 1 mark — current flows in opposite directions on each side of coil, 1 mark — opposite forces on each side create a turning effect/torque, 1 mark — use Fleming's left-hand rule to determin

Exam Tips: Fleming's left-hand rule uses the LEFT hand — a very common mistake is using the right hand. | Remember the order: F irst finger = F ield, se C ond finger = C urrent, thu M b = M otion. | The force is zero when the wire is parallel to the field — it must be at an angle (perpendicular is maximum). | For the motor, always mention the split ring commutator — it's the component that keeps the motor turning. | When asked about increasing electromagnet strength, choose the most effective answer first: iron core, then more turns, then more current. | For loudspeaker questions, always link: varying current → varying force → vibrating cone → sound waves.
Common Errors: Watch Out! 1. Wrong: Using the right hand for Fleming's left-hand rule Correct: It is Fleming's LEFT-hand rule — always use your left hand. First finger = Field, seCond finger = Current, thuMb = Motion 2. Wrong: A current-carrying wire in a magnetic field always experiences a force Correct: There is NO force when the wire is parallel to the magnetic field — the wire must be at an angle to the field, and the force is maximum when perpendicular 3. Wrong: A steel core makes a better electromagnet than an iron core because steel is stronger Correct: Soft iron is better for electromagnets because it loses its magnetism quickly when the current is switched off — steel retains magnetism (it is a ha
AO3 - Reasoning & Interpretation: Analysis and Evaluation A student investigates the strength of an electromagnet by counting how many paper clips it can pick up. Results with different numbers of coil turns (at constant current 2 A): 10 turns = 3 clips, 20 turns = 6 clips, 30 turns = 9 clips, 40 turns = 11 clips, 50 turns = 12 clips. Results with different currents (at constant 30 turns): 0.5 A = 2 clips, 1.0 A = 5 clips, 1.5 A = 7 clips, 2.0 A = 9 clips, 2.5 A = 9 clips. (a) Describe the relationship between number of turns and electromagnet strength shown in the data. Is it directly proportional? Give evidence. (b) At 2.5 A, the number of clips does not increase beyond the value at 2.0 A. Suggest an explanation for this.
Stretch & Challenge (Grade 8-9):
  • Synoptic links: explain how electromagnets connects to another Physics topic you have studied
  • Real-world: research one real-world use or example of electromagnets
  • Critical: "What are the limitations of the models used in electromagnets?"

Plenary (5 minutes)

Assessment Criteria
  • Got it: Confident explanation + correct worked examples
  • Getting there: Main points OK, needs support with detail
  • Not yet: Confused on key concepts - re-run Lesson 2

Homework & Consolidation

Recommended Resources

🎓 Smart Lesson (Guided)