Conceptual Questions

  1. The lightweight glass sphere in FIGURE Q29.1 hangs by a thread. The north pole of a bar magnet is brought near the sphere.

    1. Suppose the sphere is electrically neutral. Is it attracted to, repelled by, or not affected by the magnet? Explain.

    2. Answer the same question if the sphere is positively charged.

    FIGURE Q29.1

    The figure illustrates the reaction of a suspended glass sphere to a flat magnet.

  2. The metal sphere in FIGURE Q29.2 hangs by a thread. When the north pole of a magnet is brought near, the sphere is strongly attracted to the magnet. Then the magnet is reversed and its south pole is brought near the sphere. How does the sphere respond? Explain.

    FIGURE Q29.2

    The figure illustrates the reaction of a suspended metal sphere to a flat magnet.

  3. You have two electrically neutral metal cylinders that exert strong attractive forces on each other. You have no other metal objects. Can you determine if both of the cylinders are magnets, or if one is a magnet and the other is just a piece of iron? If so, how? If not, why not?

  4. What is the current direction in the wire of FIGURE Q29.4? Explain.

    FIGURE Q29.4

    The figure illustrates the cross sectional view of a wire surrounded by compasses.

  5. What is the current direction in the wire of FIGURE Q29.5? Explain.

    FIGURE Q29.5

    The figure illustrates the pattern of magnetic field acting on a vertically oriented wire.

  6. What is the initial direction of deflection for the charged particles entering the magnetic fields shown in FIGURE Q29.6?

    FIGURE Q29.6

    The figure consists of two parts labeled (“a”) and (b) that illustrates the direction of moving charged particles entering a magnetic field.

  7. What is the initial direction of deflection for the charged particles entering the magnetic fields shown in FIGURE Q29.7?

    FIGURE Q29.7

    The figure consists of two parts labeled (“a”) and (b) that illustrates the direction of the charged particles entering the magnetic fields.

  8. Determine the magnetic field direction that causes the charged particles shown in FIGURE Q29.8 to experience the indicated magnetic force.

    FIGURE Q29.8

    The figure consists of two parts labeled (“a”) and (b) that illustrates magnetic force and velocity on two moving charged particles.

  9. Determine the magnetic field direction that causes the charged particles shown in FIGURE Q29.9 to experience the indicated magnetic force.

    FIGURE Q29.9

    The figure consists of two parts labeled (“a”) and (b) that illustrates magnetic force and velocity on two moving charged particles

  10. You have a horizontal cathode-ray tube (CRT) for which the controls have been adjusted such that the electron beam should make a single spot of light exactly in the center of the screen. You observe, however, that the spot is deflected to the right. It is possible that the CRT is broken. But as a clever scientist, you realize that your laboratory might be in either an electric or a magnetic field. Assuming that you do not have a compass, any magnets, or any charged rods, how can you use the CRT itself to determine whether the CRT is broken, is in an electric field, or is in a magnetic field? You cannot remove the CRT from the room.

  11. The south pole of a bar magnet is brought toward the current loop of FIGURE Q29.11. Does the bar magnet attract, repel, or have no effect on the loop? Explain.

    FIGURE Q29.11

    The figure illustrates a bar magnet placed near a current loop.

  12. Give a step-by-step explanation, using both words and pictures, of how a permanent magnet can pick up a piece of nonmagnetized iron.