| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: Describe how the magnetic effect of a current is used in relays and loudspeakers and give examples of their application |
Learning Objective/s:
- Describe how the magnetic effect of a current produces mechanical motion in relays and loudspeakers.
- Explain the construction and operation principles of relays and loudspeakers.
- Apply the formula F = B I L to predict the force on a coil in each device.
- Compare the functions and typical applications of relays and loudspeakers.
- Evaluate real‑world examples where these devices are employed.
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Materials Needed:
- Projector and screen for diagrams and videos
- Whiteboard and markers
- Printed handouts with relay and speaker diagrams
- Sample relay and small loudspeaker (or demonstration video)
- Worksheet with practice questions
- Calculator for force calculations
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Introduction:
Begin with a short video showing a relay clicking and a speaker producing sound, prompting students to think about how electricity can cause movement. Recall the magnetic field around a current‑carrying conductor discussed in the previous lesson. Explain that today they will explore how this magnetic effect is harnessed in relays and loudspeakers and what they should be able to describe and compare by the end of class.
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Lesson Structure:
- Do‑now (5'): Write the force formula F = B I L and label each variable.
- Mini‑lecture (10'): Review magnetic effect and introduce relay principle with diagram.
- Demonstration (8'): Show a relay in operation and discuss its components.
- Group activity (12'): Students label a relay diagram and complete a worksheet comparing it to a loudspeaker.
- Lecture (10'): Explain loudspeaker construction and operation; show video of diaphragm movement.
- Guided practice (10'): Calculate forces for given current and field values for both devices.
- Class discussion (5'): Compare applications and address misconceptions.
- Exit ticket (5'): Write one similarity and one difference between relays and loudspeakers.
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Conclusion:
Summarise that the magnetic effect of current enables both switching and sound production through controlled mechanical motion. Invite a few students to share their exit‑ticket responses to reinforce the comparison. Assign homework to research another device that uses the same principle, such as an electromechanical buzzer, and prepare a brief description for the next lesson.
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