ASVAB ASVAB Electronics Fundamentals and Circuits 4 — Questions and Answers
Question 1: A transformer has a primary winding of 200 turns and a secondary winding of 50 turns. If the primary voltage is 120V, what is the secondary voltage?
- 480V
- 60V
- 30V (Correct answer)
- 15V
Correct answer: 30V
The turns ratio is 200:50 = 4:1, so secondary voltage = 120V ÷ 4 = 30V.
Question 2: Which type of capacitor is polarized and must be installed with correct polarity?
- Ceramic disc capacitor
- Mica capacitor
- Electrolytic capacitor (Correct answer)
- Film capacitor
Correct answer: Electrolytic capacitor
Electrolytic capacitors are polarized due to their oxide layer construction and will be damaged if installed backwards.
Question 3: In a purely inductive AC circuit, the current lags the voltage by how many degrees?
- 0°
- 45°
- 90° (Correct answer)
- 180°
Correct answer: 90°
In a purely inductive circuit, the inductor causes current to lag the applied voltage by exactly 90 degrees.
Question 4: What does a diode's 'forward voltage drop' refer to?
- The voltage needed to reverse-bias the diode
- The minimum voltage required for the diode to conduct in the forward direction (Correct answer)
- The maximum reverse voltage before breakdown
- The voltage drop across the internal resistance
Correct answer: The minimum voltage required for the diode to conduct in the forward direction
Forward voltage drop is the minimum voltage across a forward-biased diode needed for it to conduct; typically ~0.7V for silicon.
Question 5: Two capacitors of 4μF and 12μF are connected in series. What is the total capacitance?
- 16μF
- 8μF
- 3μF (Correct answer)
- 48μF
Correct answer: 3μF
Series capacitance: 1/C = 1/4 + 1/12 = 3/12 + 1/12 = 4/12, so C = 12/4 = 3μF.
Question 6: What is the primary function of a zener diode in a circuit?
- Amplify AC signals
- Regulate voltage by maintaining a constant reverse breakdown voltage (Correct answer)
- Convert AC to DC
- Store electrical charge
Correct answer: Regulate voltage by maintaining a constant reverse breakdown voltage
A zener diode is designed to operate in reverse breakdown, holding a steady voltage and thus regulating circuit voltage.
Question 7: If a resistor is color-coded yellow, violet, orange, gold, what is its resistance value?
- 4,700Ω ±5%
- 47,000Ω ±5% (Correct answer)
- 470Ω ±5%
- 4,700Ω ±10%
Correct answer: 47,000Ω ±5%
Yellow=4, Violet=7, Orange=×1000 multiplier → 47×1000 = 47,000Ω; Gold = ±5% tolerance.
ASVAB ASVAB Electronics Fundamentals and Circuits 4
A transformer has a primary winding of 200 turns and a secondary winding of 50 turns.
If the primary voltage is 120V, what is the secondary voltage?