Chapter 19 review


    Conceptual questions
      Section 19.1
      1. Research the work of James Clerk Maxwell. What physical phenomena do his four equations describe? Why was his work so important? Use a standard format for citations in your paper.
      2. Easy A stationary electric charge is surrounded by an electric field. What kind of field surrounds a moving charge?
      3. Easy Describe how changes in the understanding of the science of electricity and magnetism led to the development of three different technologies in use today.
      4. Easy Define what the armature in a motor is. Use the words rotor and electromagnet in your definition.
      5. Easy An electromagnet is placed a few centimeters west of a compass. The compass needle deflects so that it points due west. How strong is the electromagnet’s magnetic field, compared to the Earth’s magnetic field, at the location of the compass needle?
      6. What pairs of quantities are represented?
      7. Which of the following pairs of quantities can be represented by the straight arrow I and the curved arrow II shown here?
        1. I = electric current and II = magnetic field
        2. I = magnetic field and II = electric current
        3. Both a and b are valid representations.
        4. Neither a nor b is a valid representation.
      8. A physics teacher has placed a horizontal magnetic compass next to a vertical current-carrying wire.
        1. Describe or draw how the compass points (toward the wire?, away from it?, etc.).
        2. What will the compass needle do if the teacher reverses the direction of the current?
      9. When inducing a voltage in a wire coil, to maximize the induced voltage you should ______ the number of loops and ______ the rate of flux change.
        1. decrease; decrease
        2. decrease; increase
        3. increase; decrease
        4. increase; increase
      1. In doing research for a paper, a student came across the following text: “English chemist and physicist Michael Faraday showed the connection between changes in magnetic fields and induced electric current in 1822.” Which of the following are appropriate ways to include this information in the paper without plagiarizing?
        1. Include the sentence word for word, without quotations, followed by a superscript footnote number such as 10.
        2. Include the sentence word for word, enclose the words with quotation marks, and follow the text with a citation to the book (enclosed in parentheses).
        3. Include the sentence word for word, enclose the words with quotation marks, follow the text with a superscript number for footnoting, and include a citation to the book at the end of the paper.
      2. Easy Draw the magnetic field lines around two wires that are parallel to one another and have current flowing in the same direction. Do the two wires attract or repel, provided they are close enough together?
      3. Medium Explain how a tangent is used to determine the direction of a magnetic field near a current-carrying wire.
      4. Medium A horizontal wire entering a hole in a wall carries electric current. Using a diagram, show the direction of the magnetic field around the wire if the current travels into the wall. Use a second diagram to show the magnetic field direction if the current flows away from the wall.
      5. Medium Research and describe the contributions of three scientists to the understanding of the connection between electricity and magnetism.
      6. Challenging Joe and Sarah are experimenting with electricity and magnetism. Both are carrying handheld magnetic field detectors; Joe is wearing a sweater that has become electrically charged. When Joe runs past Sarah, she detects a slight magnetic field, but he doesn’t. What’s going on?
      Section 19.2
      1. Which of the following statements is the best description of the following equation? emf=N Δ Φ B Δt
        1. Changing emf will cause the magnetic flux to change in a coil.
        2. Changing magnetic flux will induce an emf in a coil.
        3. Changing magnetic field will cause an electromotive current to flow.
        4. Induced emf will change the magnetic flux in a coil.

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