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1. A potential difference of 1.5 V is induced in a coil of wires when a magnet is plunged into the
coil. The coil has 500 turns of wire in it. What is the new potential difference if:
a) the number of turns of wire is reduced to 250?
b) the speed of the plunge is doubled?
c) the magnet used is replaced with a magnet which produces a field three times as strong?
d) the changes outlined in (a), (b), and (c) are all produced at the same time?
2. A 500 turn coil is connected to a galvanometer. A magnet is plunged into the coil, which results
in a current of 8.0 mA. The resistance of the galvanometer and coil is 100 W. After performing
this experiment, the 500 turn coil is replaced with a 1500 turn coil. The new resistance of the
galvanometer and coil now increases to 150 W. If the same magnet is again plunged into the
coil with the same speed, determine what the new current will be.
3. For each of these circumstances, determine the direction of the induced magnetic field, and
the direction of the induced current.
4. a) The following diagram shows the direction of motion of a conductor between the jaw's of a
magnet. What is the direction of the induced current in the conductor?
b) Given the direction of motion of the magnet in the diagram below, what is the direction of
the current in the coil?
5. a) Describe the differences between an AC and DC generator.
b) Describe the difference in current flow through the armature coil of AC and DC generators.
c) For DC generators, what is the relationship between the number of coils on the armature,
and the number of segments on the commutator?
6. a) Draw a labeled diagram of an AC generator. Describe the role of each of the major parts
of this generator.
b) For the AC generator you have drawn, use Lenz's Law to explain the direction of induced
current for one complete cycle of the armature.
c) List the factors which affect the potential difference produced by an AC generator.
7. Determine the wavelength of cosmic rays with a frequency of 1 X 1026 Hz.
8. A feature on the Martian surface has a length of 8.0 X 103 km. Determine how many
wavelengths of electromagnetic waves of frequency 60 Hz, fit into this feature.
9. An electromagnetic wave from the sun is traveling straight down towards the equator. If the
wave is polarized with the electric field oriented in an east-west plane, what is the direction of
the oscillations of the magnetic field?
10. Explain why AM radio reception is better than FM radio reception between buildings of a
large city.
11. Make the following calculations.
a) What is the frequency of a microwave with wavelength of 1.8 cm?
b) A radar signal has a frequency of 3.2 X 1010 Hz. What is the wave's wavelength?
c) The electromagnetic waves emitted from electrical transmission lines has a frequency
of 60 Hz. What is the distance between successive maximums of the oscillating electric
fields of such a wave?
d) Red light has a wavelength of 6.50 X 10-7 m. What is its frequency?
12. A hockey game is being played in Montreal. The game is being watched on television by a fan
in Montreal and one in Los Angeles which is approximately 6000 km away. The signal is sent
to Los Angeles by microwaves, which are sent first to a satellite 36 000 km above the Earth,
and then from the satellite back to Earth. By making reasonable assumptions, determine how
much sooner the Montreal fan hears the results than the Los Angeles fan.
13. Explain why X-rays can be used to take photographs of internal structures of a human body.
14. Explain why an unborn developing human should not be X-rayed.
15. When cancer is treated by exposing the malignant cell to X-rays, there are often side effects.
These effects include such things as loss of hair, dizziness, and lack of energy. Explain why
these side effects occur.
16. Spectral analysis can be used to determine many things about distant stars. One such thing is
a determination of the stars surface temperature. How do astronomers determine this surface
temperature?
17. Photographers require special xenon flash bulbs in order to get good pictures indoors with
normal daylight film. These bulbs have a filament that reach an average temperature of
6000 K. If these pictures are taken with normal lighting, such as incandescent lights or
fluorescent lights, the colors on the photograph do not turn out properly. The temperature
of an incandescent bulb is about 2500 K, and the temperature of a fluorescent light can be
considered to be about 3500 K. Normal sunlight produces good pictures with daylight film,
and the sun's average surface temperature is 6000 K. If you are using daylight film, why
don't pictures turn out with incandescent or fluorescent lighting, but will turn out with xenon
flash bulbs?
18. The frequencies of ultrasonic waves used to observe unborn developing humans have
frequencies of 30 000 Hz to 45 000 Hz.
a) If ultrasonic waves were electromagnetic waves, what would be a typical wavelength
for them?
b) In reality, ultrasonic waves are sound waves. If the speed of these waves was 340 m/s,
what would be the true wavelength of the waves?
January 19, 2014
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