Electromagnetic Induction
Overview
Every time you charge a phone, ride in an electric car, or flick on a light switch, you rely on electromagnetic induction. This single principle - a changing magnetic field producing a voltage - underpins generators, transformers, and the entire electricity supply chain from power station to wall socket.
In this lesson you will learn how moving a conductor through a magnetic field induces a voltage, what determines the size of that voltage, how AC generators and transformers exploit the effect, and why the National Grid transmits electricity at extremely high voltages. These ideas are tested heavily on Edexcel Papers 1 and 2, often as structured calculation and extended-writing questions.
Objectives
- Know that a voltage is induced in a conductor or a coil when it moves through a magnetic field or when a magnetic field changes through it and describe the factors that affect the size of the induced voltage
- Describe the generation of electricity by the rotation of a magnet within a coil of wire and of a coil of wire within a magnetic field, and describe the factors that affect the size of the induced voltage
- Describe the structure of a transformer and understand that a transformer changes the size of an alternating voltage by having different numbers of turns on the input and output sides
- Explain the use of step-up and step-down transformers in the large-scale generation and transmission of electrical energy
- Know and use the relationship between input (primary) and output (secondary) voltages and the turns ratio for a transformer: input voltage / output voltage = primary turns / secondary turns
- Know and use the relationship: input power = output power, VpIp = VsIs for 100% efficiency
Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Electromagnetic Induction. 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.
- A magnet is pushed into a coil of wire connected to a voltmeter. What happens when the magnet is held stationary inside the coil? A) The voltage increases B) The voltage stays constant C) The voltage drops to zero D) The voltage reverses Answer: C
- Which change would increase the voltage induced in a coil by a moving magnet? A) Using a weaker magnet B) Moving the magnet more slowly C) Increasing the number of turns on the coil D) Reducing the area of the coil Answer: C
- A transformer has 100 turns on the primary coil and 500 turns on the secondary coil. If the input voltage is 20 V, what is the output voltage? A) 4 V B) 20 V C) 100 V D) 500 V Answer: C
- Electricity is transmitted at high voltage across the National Grid primarily to: A) Make the current larger B) Reduce the resistance of the cables C) Reduce the current and therefore reduce power loss D) Increase the speed of electricity through the wires Answer: C
- A transformer works with alternating current but not with direct current because: A) DC produces too much heat B) DC cannot flow through a coil C) DC produces a constant magnetic field that does not induce a voltage in the secondary coil D) DC would melt the iron core Answer: C
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Recommended Books
Practice Mock Questions
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