Electromagnetic Induction
Übersicht
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.
Ziele
- 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
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Unterrichtsbewertung
Herzlichen Glückwunsch zum Abschluss der Lektion über Electromagnetic Induction. Jetzt, da Sie die wichtigsten Konzepte und Ideen erkundet haben,
Sie werden auf eine Mischung verschiedener Fragetypen stoßen, darunter Multiple-Choice-Fragen, Kurzantwortfragen und Aufsatzfragen. Jede Frage ist sorgfältig ausgearbeitet, um verschiedene Aspekte Ihres Wissens und Ihrer kritischen Denkfähigkeiten zu bewerten.
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- 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
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Weiterlernen mit offenen Quellen
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Lehrbuchabschnitt
Motors, Generators, and Transformers
Explain how electric motors, generators, and transformers work
"Physics: Motors, Generators, and Transformers" 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/20-2-motors-generators-and-transformers. Access for free at https://openstax.org/books/physics/pages/1-introduction
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Lehrbuchabschnitt
Transformers
Transformers do what their name implies—they transform voltages from one value to another (The term voltage is used rather than emf, because transformers have internal resistance). For example, many cell phones, laptops, video games, and power tools and small appliances have a transformer built into
"College Physics: Transformers" 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/23-7-transformers. Access for free at https://openstax.org/books/college-physics/pages/1-introduction
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