Download Chapter 8: Electromagnetism End of Chapter Questions

Chapter 8: Electromagnetism
End of Chapter Questions
1. By whom, and in what setting, was the relationship between electricity and magnetism
discovered?
2. The force between electrically charged particles depends on the magnitude of charge, the
distance of separation, and what else?
3. What is the source of magnetic force?
4. Is the rule for the interaction between magnetic poles similar to the rule for the interaction
between electrically charged particles?
5. In what way are magnetic poles very different than electric charges?
6. An electric field surrounds an electric charge. What additional field surrounds it when it moves?
7. What produces a magnetic field?
8. What two kinds of rotational motion are exhibited by electrons in an atom?
9. In Chapter 6 we learned that the electric field is radially directed about a point charge. What is the
direction of the magnetic field surrounding a current-carrying wire?
10. What happens to the direction of the magnetic field about an electric current when the direction of
the current is reversed?
11. Both gravitational and electrical forces act along the direction of the force fields. How does the
direction of the magnetic force on a moving charged particle differ?
12. What effect does the earth's magnetic field have on the intensity of cosmic rays striking the
earth's surface?
13. Exactly what was it that Michael Faraday and Joseph Henry discovered?
14. Why is it more difficult to thrust a magnet into a coil of many loops compared with a single loop?
15. What must change in order for electromagnetic induction to occur?
16. In addition to induced voltage, what does the current produced by electromagnetic induction
depend?
17. What are the three ways that voltage can be induced in a wire?
18. How does the frequency of induced voltage compare to how frequently a magnet is plunged in
and out of a coil of wire?
19. What is the basic similarity between a generator and an electric motor?
20. What is the basic difference between a generator and an electric motor?
21. Why does a generator produce alternating current?
22. Is electromagnetic induction a key feature of a transformer?
23. Why does a transformer require alternating current?
24. What is the principal advantage of ac over dc?
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Hans Christian Oersted, in 1820, in a classroom.
The force depends on motion.
The source of magnetic force is the motion of charged particles, usually electrons.
Yes, the rule for magnetic poles, "like poles repel; opposite poles attract," is similar to the electrical rule, "like charges repel
one another and unlike charges attract."
Whereas electric charges can be isolated, magnetic poles cannot.
A magnetic field.
A magnetic field is produced by electric charge in motion.
The spinning motion and the orbital motion of electrons.
Surrounding a current-carrying wire, the magnetic field forms concentric circles about the wire.
The magnetic field reverses direction also.
The direction of the magnetic force is always perpendicular to both the magnetic field lines and the velocity of the charged
particle.
Cosmic rays are deflected by the earth's magnetic field, reducing their intensity at the earth's surface.
They both discovered that electric current can be produced in a wire simply by moving a magnet in or out of a coiled part of
the wire.
More loops means more voltage, which means we do more work to induce it–more loops means more electromagnets to
push against.
The magnetic field must change to induce electromagnetic induction.
The resistance of the coil and the circuit to which it is connected.
By moving the loop near a magnet, by moving a magnet near the loop, or by changing a current in a nearby loop.
The same, for the frequency of the alternating voltage induced equals the frequency of the changing magnetic field.
The construction of each is identical. They look the same.
The roles of input and output are reversed. In a motor, electric energy is the input and mechanical energy the output; in a
generator, mechanical energy is the input and electric energy the output.
Because the changing magnetic field alternates, making the induced voltage alternate, which makes the current alternate.
Yes, indeed.
Alternating current provides the necessary ingredient for induction–change.
The ease with which voltages can be stepped up or down with a transformer.