ASVAB Electronics Practice Test 1 2 — Questions and Answers
Question 1: A circuit has a resistance of 10 ohms and a current of 3 amperes flowing through it. What is the voltage across the resistor?
- 3.3 volts
- 13 volts
- 30 volts (Correct answer)
- 0.3 volts
Correct answer: 30 volts
Ohm's Law states V = I × R. Substituting the given values: V = 3 A × 10 Ω = 30 volts. Ohm's Law is the most fundamental relationship in electronics, connecting voltage (V), current (I), and resistance (R).
Question 2: What is the primary function of a capacitor in an electronic circuit?
- To amplify the current flowing through the circuit
- To store electrical energy in an electric field and release it (Correct answer)
- To convert AC voltage to DC voltage
- To limit the current to a safe level
Correct answer: To store electrical energy in an electric field and release it
A capacitor stores energy in the electric field between two conductive plates separated by an insulating material (dielectric). It can charge (store) and discharge (release) energy rapidly, making it useful for filtering, timing, and energy storage applications.
Question 3: In a parallel circuit with three branches, if one branch is open (broken), what happens to the other two branches?
- All current stops flowing in the entire circuit
- The voltage across the remaining branches drops to zero
- The remaining two branches continue to operate normally (Correct answer)
- The resistance of the remaining branches doubles
Correct answer: The remaining two branches continue to operate normally
In a parallel circuit, each branch has its own independent path back to the voltage source. If one branch opens (breaks), the other branches are unaffected — they still have complete paths and continue to operate at the same voltage. This is a key advantage of parallel wiring used in homes.
Question 4: A transformer steps voltage up from 120V to 480V. If the primary coil has 200 turns, how many turns does the secondary coil have?
- 50 turns
- 200 turns
- 400 turns
- 800 turns (Correct answer)
Correct answer: 800 turns
The transformer turns ratio formula is: V1/V2 = N1/N2. So N2 = N1 × (V2/V1) = 200 × (480/120) = 200 × 4 = 800 turns. Transformers work on electromagnetic induction and can only operate with AC because DC does not produce a changing magnetic field.
Question 5: Which electronic component allows current to flow in only one direction?
- Resistor
- Capacitor
- Diode (Correct answer)
- Inductor
Correct answer: Diode
A diode is a semiconductor device that acts like a one-way valve for electrical current — it conducts in the forward-biased direction and blocks current in the reverse-biased direction. Diodes are used in rectifiers to convert AC to DC, in signal detection, and in protection circuits.
Question 6: What does an inductor do when the current through it suddenly increases?
- It instantly allows the increased current to pass through unchanged
- It opposes the change in current by generating a back electromotive force (EMF) (Correct answer)
- It stores the extra current as an electric charge
- It converts the current increase into a voltage decrease
Correct answer: It opposes the change in current by generating a back electromotive force (EMF)
An inductor opposes changes in current — this property is called inductance. When current increases, the magnetic field around the coil changes, inducing a back EMF (by Lenz's Law) that opposes the increase. This makes inductors useful in filtering AC ripple, smoothing power supplies, and blocking high-frequency signals.
ASVAB Electronics Practice Test 1 2
A circuit has a resistance of 10 ohms and a current of 3 amperes flowing through it.
What is the voltage across the resistor?