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Physics Core/AP 1 and 2

Chapter 21: 1-5 Assignment

Course Materials are always under revision! Weblecture content may change anytime prior to two weeks before scheduled chat session for content.

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Homework

Physics 21: 1-5 Induced Current

Homework

Reading Preparation

Text Reading: Giancoli, Physics - Principles with Applications, Chapter 21: 1 to 5

Study Points

Key Equations

Magnetic Flux Φ B   =   B A   =   BA   cos   θ    Flux is determined from the amount owed magnetic field passing through "surface" area in a direction perpendicular to the plane of the area. Flux is always "normal" to the area.
Faraday's Law of Induction ℰ  = N Δ Φ B Δ t   Remember that emf Ɛ is not a force. It is the potential difference between two terminals of any device that transforms some other type of energy (chemical, mechanical) into electrical energy. When the electrical source is a battery, Ɛ is the voltage of the battery. When the electrical source is a changing magnetic field, the magnitude of the resulting Ɛ through a single loop of wire depends on the rate at which the magnetic field (as measured by its flux through the area enclosed by the wire) is changing. If we have multiple loops of wire, the induced Ɛ through each wire is the same; so we can increase the net Ɛ by coiling the wire many times.
Lenz's lawDetermines direction of current flow from ƐThe direction of the induced Ɛ will create a magnetic field that opposies the original change in flux.
Electric field induced by magnetic field E   =   F q   =   qvB q   =   vB The field induced by a charge moving through a magnetic field depends on its velocity

Web Lecture

Read the following weblecture before chat: Electromagnetic Induction

Study Activity

Use the simulation below to explore the action of Faraday's Law.

  • Turn on the Field lines.
  • What happens to the current and voltage in the circuit as you do each of the following actions?
    • Grab the magnet and move it to a position above the coil so that at most one field line passes through or below the coil. Move the magnet back and forth (left to right) slowly, then quickly.
    • Move the magnet so that it is above the coil with two field lines through the coil and repeat your motion tests.
    • Move the magnet so that it is within the coil and repeat your motion tests.
    • Use the bar magnet button to revers the magnet polarity. What happens as you repeat your tests?
    • Change to the double coil setup and repeat your motion tests. When is the light brightest and current highest? How does the number of coils affect the current flow?

Physics simulation Java Applets are the product of the PHET Interactive Simulations project at the University of Colorado, Boulder.

Chat Preparation Activities

Chapter Quiz

Lab Work

If you want lab credit for this course, you must complete at least 12 labs (honors course) or 18 labs (AP students). One or more lab exercises are posted for each chapter as part of the homework assignment. We will be reviewing lab work at regular intervals, so do not get behind!