Suppose a current-carrying wire has a cross-sectional area that gradually becomes smaller along the wire so that the wire has the shape of a very long, truncated cone. How does the drift speed vary along the wire?
1.It slows down as the cross section becomes smaller.
2.It speeds up as the cross section becomes smaller.
3.It doesn't change.
4.More information is needed.
2
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Suppose we wrap a solenoid coil around a hollow cardboard cylinder. Now suppose that we insert an iron core into the solenoid. What will happen to the coil’s inductance when we insert the iron core? (Explain.)
A. The inductance increases. B. The inductance decreases. C. The inductance is unchanged. D. One needs more information to answer the question.
Whirl a rock at the end of a string and it follows a circular path. If the string breaks, the rock tends at first to
A) continue in a circular path. B) follow a straight-line path. C) spiral inward. D) fall straight downward.
Which of these, both of the same length, has the greater electrical resistance?
A) a thick copper wire B) a thin copper wire C) both about the same D) need more information
The current in a coil with a self-inductance of 1.5 mH increases from 0 to 2.0 A in a tenth of a second. What is the induced emf in the coil?
a. 15 mV c. 0.10 V b. 0.30 V d. 30 mV