Electromagnetism
Overview
Every electric motor, every loudspeaker and every MRI scanner relies on the same principle: a current flowing through a magnetic field experiences a force. Electromagnetism connects electricity to magnetism and puts that connection to work in devices you use every day.
In this lesson you will trace the magnetic field around a current-carrying wire, build it into a solenoid, strengthen it into an electromagnet, and then apply Fleming's left-hand rule to predict forces. You will see how those forces drive a d.c. motor and make a loudspeaker cone vibrate to produce sound.
Objectives
- Know that an electric current in a conductor produces a magnetic field around it
- Describe the construction of electromagnets
- Draw magnetic field patterns for a straight wire, a flat circular coil and a solenoid when each is carrying a current
- Know that there is a force on a charged particle when it moves in a magnetic field as long as its motion is not parallel to the field
- 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.
- What shape is the magnetic field around a straight current-carrying wire? A) Straight parallel lines B) Concentric circles C) Radial lines pointing outward D) A single loop Answer: B
- Which of the following will NOT increase the strength of an electromagnet? A) Increasing the current B) Adding more turns to the coil C) Using a copper core D) Using a soft iron core Answer: C
- In Fleming's left-hand rule, what does the thumb represent? A) Current B) Magnetic field C) Force D) Voltage Answer: C
- A wire carries a current of 6.0 A through a 0.50 T field. The wire is 0.20 m long. What is the force on the wire? A) 0.06 N B) 0.60 N C) 6.0 N D) 60 N Answer: B
- What is the role of the split-ring commutator in a d.c. motor? A) It increases the current B) It reverses the current direction every half-turn C) It strengthens the magnetic field D) It provides the power supply Answer: B
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Recommended Books
Further learning from open sources
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Textbook section
Magnetic Fields, Field Lines, and Force
Summarize properties of magnets and describe how some nonmagnetic materials can become magnetized
"Physics: Magnetic Fields, Field Lines, and Force" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/physics/pages/20-1-magnetic-fields-field-lines-and-force. Access for free at https://openstax.org/books/physics/pages/1-introduction
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Textbook section
Torque on a Current Loop: Motors and Meters
Motors are the most common application of magnetic force on current-carrying wires. Motors have loops of wire in a magnetic field. When current is passed through the loops, the magnetic field exerts torque on the loops, which rotates a shaft. Electrical energy is converted to mechanical work in the
"College Physics: Torque on a Current Loop: Motors and Meters" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/college-physics/pages/22-8-torque-on-a-current-loop-motors-and-meters. Access for free at https://openstax.org/books/college-physics/pages/1-introduction
Published by other organisations under open licences, credited as they ask. Links open their websites.
Practice Mock Questions
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