Chapter 21: Q12CQ (page 771)
Some light bulbs have three power settings (not including zero), obtained from multiple filaments that are individually switched and wired in parallel. What is the minimum number of filaments needed for three power settings?
Three power settings can be obtained from a minimum of 2 filaments.
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Aemf automobile battery has a terminal voltage ofwhen being charged by a current of.(a) What is the batteryโs internal resistance?(b) What power is dissipated inside the battery?(c) At what rate (in ยบC/min) will its temperature increase if its mass isand it has a specific heat of, assuming no heat escapes?
(a) What is the terminal voltage of a large 1.54 v carbon-zinc dry cell used in a physics lab to supply 2.00 a to a circuit, if the cell's internal resistance is ? (b) How much electrical power does the cell produce? (c) What power goes to its load?
Some strings of holiday lights are wired in series to save wiring costs. An old version utilized bulbs that break the electrical connection, like an open switch, when they burn out. If one such bulb burns out, what happens to the others? If such a string operates on 120 V and has 40 identical bulbs, what is the normal operating voltage of each? Newer versions use bulbs that short circuit, like a closed switch, when they burn out. If one such bulb burns out, what happens to the others? If such a string operates on 120 V and has 39 remaining identical bulbs, what is then the operating voltage of each?
Suppose you measure the terminal voltage of an1.585-V alkaline cell having an internal resistance ofby placing arole="math" localid="1656394302991" voltmeter across its terminals. (See Figure 21.54.) (a) What current flows? (b) Find the terminal voltage. (c) To see how close the measured terminal voltage is to the emf, calculate their ratio.
Two resistors, one having a resistance of , are connected in parallel to produce a total resistance of . (a) What is the value of the second resistance? (b) What is unreasonable about this result? (c) Which assumptions are unreasonable or inconsistent?
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