ASVAB Electronics Information Practice Test 3: Batteries, Magnetism and Semiconductors
- Batteries, Magnetism, Semiconductors and Energy Use
- 10 questions
- 15 minutes
These questions go beyond Ohm's law into batteries, magnetism, semiconductors and energy use. When a question gives watts and hours, convert to kilowatt-hours before you compare.
Tap an option to mark your answer. You can change your mind, or tap the same option again to leave the question blank. The correct answers and explanations appear when you finish the test.Tap an option to answer; tap it again to leave the question blank.
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Question 1
Four 1.5-volt batteries are connected in series. What is the total voltage?
Correct answer: B
In series, battery voltages add: 4 × 1.5 = 6 volts. The answer 1.5 volts is what you get when the batteries are connected in parallel.
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Question 2
Two identical 1.5-volt batteries are connected in parallel to a small lamp. Compared with one battery alone, what changes?
Correct answer: D
Parallel batteries keep the same voltage but share the current, so together they run the lamp longer. Doubling the voltage requires a series connection.
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Question 3
A wire carries an electric current. What is created around the wire?
Correct answer: A
Any electric current produces a magnetic field around the conductor, which is the principle behind electromagnets and motors. A static charge is a charge at rest, not a moving current.
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Question 4
Which change will make an electromagnet stronger?
Correct answer: C
More turns, more current or an iron core all strengthen an electromagnet. A wooden core does not concentrate the magnetic field the way iron does.
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Question 5
Why will a transformer not work when it is connected to a steady DC source such as a car battery?
Correct answer: B
A transformer works only when the current in the primary coil keeps changing, which induces voltage in the secondary. Steady DC makes a constant field, so nothing is induced.
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Question 6
Resistors of 6 ohms, 3 ohms and 2 ohms are connected in parallel. What is their combined resistance?
Correct answer: A
1/R = 1/6 + 1/3 + 1/2 = 1/6 + 2/6 + 3/6 = 1, so R = 1 ohm. Adding the values to get 11 ohms is the rule for series, not parallel.
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Question 7
A 200-watt television is used for 5 hours every day for 30 days. How much energy does it use in that time?
Correct answer: D
200 W × 5 h × 30 days = 30,000 watt-hours = 30 kWh. The answer 1 kWh is the use for a single day.
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Question 8
Which element is most widely used to make the semiconductor chips in computers?
Correct answer: C
Silicon is a semiconductor whose conductivity can be controlled by adding small amounts of other elements. Copper and aluminum are good conductors used for wiring, not for transistors themselves.
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Question 9
A technician connects an LED to a battery through a correct resistor, but the LED does not light. The LED is not damaged. What is the most likely cause?
Correct answer: B
An LED is a diode, so current flows only when it is connected with the correct polarity. A resistor value that is too low or a voltage that is too high would make it too bright or burn it out, not keep it dark.
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Question 10
Several bulbs are wired in a single series loop. One bulb burns out. What happens to the other bulbs?
Correct answer: A
A series circuit has only one path, so a burned-out bulb opens the circuit and stops all current. In a parallel circuit the other bulbs would stay lit.
Questions you leave blank are not counted as wrong.
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