If you’re planning on taking the ASVAB Electronics Information Technical Subtest, check out these practice questions!
A: Inductors resist changes in current and for this reason act as resistors in alternating current circuits. However, this property is also important in a direct current circuit as seen here. An open circuit has no current, but the moment the switch is closed, current will begin to flow. The inductor, resisting the sudden change in voltage, will resist current flow at first. The lamp, since it is parallel to the resisting inductor, will light up immediately without difficulty. However, the inductor will soon “get used” to the current flow, and the resistance of its path will drop significantly. As more current flows through the easy inductor path, the total current (and therefore energy use) of the circuit will increase significantly as the overall resistance drops. (D) is exactly the opposite of what will happen. Something similar to (B) could happen only if the voltage source were limited in the amount of current it could provide and the small fraction of current passing through the lamp were not enough to light the lamp once the inductor dropped its resistance, or if the total current draw caused a fuse or breaker to cut off the current. However, in neither of these cases would the lamp itself “burn out.”
D: You can dismiss (A) and (B), since for loads in parallel, the voltage drop is the same across all paths; the brightness of the light would not change if the lamp were wired in parallel with either a capacitor or an inductor. Loads in series, on the other hand, affect the overall resistance of the circuit and therefore the total power draw on the battery. Recall that capacitors and inductors can either let current flow freely or act as resistors, depending on the type of current. In an AC circuit, a capacitor lets current flow freely while an inductor resists current flow. An inductor placed in series with the lamp will therefore act as a resistor over which a voltage drop occurs, and the lamp will be correspondingly dimmer than if the voltage drop of the circuit occurred entirely over the lamp itself.
C: The choices represent four different capacitor symbols: a fixed capacitor (A), variable capacitor (B), polarized capacitor (C), and trimmer capacitor (D).
B: The first and second color determine digits, and the last one determines how many zeroes to add. Black is zero, then orange (in either of the first two positions) is three, and then orange (in the final position) is three zeroes. A zero at the beginning of the number has no effect, as 03000 is just written as 3,000. Answer choice (C) would have been correct if the pattern were orange, black, and then orange.
B: In the symbol, the number 2 indicates the collector.