Electromagnetism
Overview
Every fan, every washing machine drum and every loudspeaker cone moves for the same reason: a wire carrying a current, sitting in a magnetic field, gets pushed. Nothing touches it, and the push can be reversed by flicking a switch.
In this lesson you will see how a current creates a magnetic field of its own, why that field makes the wire feel a force when it meets another one, how to predict which way the force acts using Fleming's left-hand rule, and how motors and loudspeakers put the effect to work.
Objectives
- Know that an electric current in a conductor produces a magnetic field around it
- Understand why a force is exerted on a current-carrying wire in a magnetic field, and how this effect is applied in simple d.c. electric motors and loudspeakers
- Use the left-hand rule to predict the direction of the resulting force when a wire carries a current perpendicular to a magnetic field
- Describe how the force on a current-carrying conductor in a magnetic field changes with the magnitude and direction of the field and current
Mind map
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Flashcards
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Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Electromagnetism. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- The magnetic field around a long straight current-carrying wire is: A) Straight lines along the wire B) Circles centred on the wire C) The same shape as a bar magnet field D) Uniform in all directions Answer: B
- Fleming's left-hand rule is used to find the direction of the: A) Magnetic field around a wire B) Current induced in a moving wire C) Force on a current-carrying wire in a magnetic field D) Current in a transformer Answer: C
- In Fleming's left-hand rule, the first finger represents the: A) Force B) Field C) Current D) Motion Answer: B
- The current in a wire between the poles of a magnet is reversed and the magnet is also turned round. The force on the wire: A) Is unchanged in direction B) Reverses direction C) Becomes zero D) Doubles in size Answer: A
- The force on a current-carrying wire in a magnetic field is zero when the wire is: A) At right angles to the field B) Parallel to the field C) Carrying a large current D) Between strong magnets Answer: B
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Practice Mock Questions
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