ASVAB Electronics 5 — Questions and Answers
Question 1: Which semiconductor device can be used to amplify a signal using three terminals: gate, source, and drain?
- MOSFET (Correct answer)
- BJT transistor
- SCR
- DIAC
Correct answer: MOSFET
A MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) uses gate, source, and drain terminals and controls current via an electric field.
Question 2: In a full-wave bridge rectifier, how many diodes are required?
- 4 (Correct answer)
- 1
- 2
- 6
Correct answer: 4
A bridge rectifier uses 4 diodes arranged in a bridge configuration to convert both half-cycles of AC into DC.
Question 3: What does the term 'gain' mean in the context of an amplifier?
- The ratio of output signal amplitude to input signal amplitude (Correct answer)
- The maximum voltage the amplifier can handle
- The frequency at which the amplifier operates
- The power consumed by the amplifier
Correct answer: The ratio of output signal amplitude to input signal amplitude
Gain is the ratio of output to input (voltage, current, or power), indicating how much the amplifier increases the signal.
Question 4: A fuse is rated at 5 amps. If the circuit draws 7 amps, what will happen?
- The fuse will blow, opening the circuit (Correct answer)
- The fuse will increase its rating automatically
- The current will be reduced to 5 amps
- Nothing will happen immediately
Correct answer: The fuse will blow, opening the circuit
When current exceeds the fuse rating, the fuse element melts and opens the circuit, protecting the wiring and components.
Question 5: What is the function of an oscilloscope in electronics testing?
- To display voltage waveforms as a function of time (Correct answer)
- To measure resistance of components
- To generate test signals for circuits
- To measure the inductance of coils
Correct answer: To display voltage waveforms as a function of time
An oscilloscope displays voltage versus time on a screen, allowing technicians to visualize signal shape, frequency, and amplitude.
Question 6: Which law states that the total current entering a junction equals the total current leaving the junction?
- Kirchhoff's Current Law (Correct answer)
- Ohm's Law
- Faraday's Law
- Kirchhoff's Voltage Law
Correct answer: Kirchhoff's Current Law
Kirchhoff's Current Law (KCL) states that charge is conserved at any node, so all currents entering must equal all currents leaving.
Question 7: What is the impedance of a pure inductor at DC (zero frequency)?
- Zero (short circuit) (Correct answer)
- Infinite (open circuit)
- Equal to its inductance value in ohms
- Equal to its resistance
Correct answer: Zero (short circuit)
Inductive reactance XL = 2πfL; at DC (f=0), XL = 0, so an ideal inductor is a short circuit to DC.
ASVAB Electronics 5
Which semiconductor device can be used to amplify a signal using three terminals: gate, source, and drain?