Sometimes you hear someone say that a particular appliance

Reading Check

-55. What kind of charge does an object acquire when electrons

are stripped from it?

Exercises

71. Why are objects with vast numbers of electrons normally

not electrically charged?

81. Why is a good conductor of electricity also a good conductor

of heat?

105. A car’s headlight dissipates 40 W on low beam and

50 W on high beam. Is there more or less resistance in

the high-beam filament?

Discussion Questions

109. In which of the circuits does a current exist to light the bulb?

110. Does more current “flow” out of a battery than into it?

Does more current “flow” into a lightbulb than out of

it? Explain

111. Sometimes you hear someone say that a particular appliance

“uses up” electricity. What is it that the appliance

actually consumes, and what becomes of it?

119. In the circuit shown, how do the brightnesses of the

three identical lightbulbs compare? Which lightbulb

draws the most current? What happens if bulb A is

unscrewed? If bulb C is unscrewed?

Chapter9

Reading Check-

77. Why is iron magnetic and wood not magnetic?

Think and Solve Exercises

52. What kind of force field surrounds a stationary electric

charge? What additional field surrounds it when

it moves?

75. If your metal car moves over a wide, closed loop of wire

embedded in a road surface, is Earth’s magnetic field

within the loop altered? Does this produce a current

pulse? Can you think of a practical application at a traffic

intersection?

87. Can an efficient transformer step up energy? Defend

your answer

Discussion Questions

95. One method for making a compass is to stick a magnetized

needle into a piece of cork and float it in a glass bowl full of

water, as shown. The needle aligns itself with the horizontal

component of Earth’s magnetic field. As the north pole of

this compass is attracted northward, does the needle float

toward the north side of the bowl? Defend your answer

103. Discuss what is wrong with this scheme. To generate

electricity without fuel, arrange a motor to run a generator

that produces electricity that is stepped up with

transformers so that the generator can run the motor

and simultaneously furnish electricity for other uses.

References