DC Electric Circuits
Suppose an inductor is connected to a variable current source, where the current is steadily increased at a rate of 1.5 amps per second. How much voltage will the 4 Henry inductor drop, and what will be the polarity of that drop? Remember, the direction of the arrow in a current source symbol points in the direction of conventional flow, not electron flow!
In real life, an inductor will not drop the exact same amount of voltage that you will calculate here. Determine if the real voltage drop across such an inductor would be greater or less than predicted, and explain why.
Two 5 H inductors connected in series are subjected to an electric current that changes at a rate of 4.5 amps per second. How much voltage will be dropped across the series combination?
Now suppose that two 5 H inductors connected in parallel are subjected to the same total applied current (changing at a rate of 4.5 amps per second). How much voltage will be dropped by these inductors? Hint: the total current is divided evenly between the two inductors.
Suppose a short-circuit were to develop in this electric power system:
The purpose of the circuit breaker, of course, is to open the circuit automatically, to prevent damage to the power conductors. In a large electric power system, the magnitudes of such short-circuit currents can be enormous.
Large inductors, commonly called reactors, are often installed in series with power conductors in high-voltage power systems in order to “soften” the onset of short-circuit currents:
Explain how the addition of a “reactor” helps to minimize the magnitude of the short-circuit current the breaker has to interrupt.
Small inductors often look like resistors, even to the extent that their values are designated by colored bands. Determine the values of the following inductors (express the tolerance as a percentage), based on their color codes:
- Red, Grn, Brn, Gld
- Wht, Org, Red, Sil
- Grn, Gry, Blk
- Vio, Blu, Org, Gld
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