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ASVAB Study Guide

Electronics Information (EI)

Electronics Information (EI) tests basic electricity and electronics. A lot of it is vocabulary and recognition, with some short Ohm's-law calculations. It's key for electronics, avionics and communications jobs.

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Ohm's law and power

Learn these cold: voltage = current × resistance (V = I × R), so I = V ÷ R and R = V ÷ I. Power P = V × I (and P = I² × R). Most EI calculations are one of these.

Circuits

Series: the same current flows everywhere and resistances add. Parallel: the voltage is the same across each branch, the branch currents add, and total resistance drops below the smallest resistor. Know open vs. short circuits and grounding.

Components and symbols

Know what each part does: resistor (limits current), capacitor (stores charge), inductor, transformer (changes AC voltage), diode (one-way flow), transistor (switch/amplify), fuse and relay. Learn their schematic symbols. Know conductors vs. insulators vs. semiconductors.

Units and safety

Volt (V), amp (A), ohm (Ω), watt (W), farad (F), hertz (Hz). Know AC vs. DC and frequency. Understand fuses, breakers and grounding for safety.

Key takeaways

  • Ohm's law (V = IR) and power (P = VI) cover most of the calculations.
  • A big part of the score is simply knowing the terms and symbols.
  • Series adds resistance; parallel lowers it.
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Free sample Electronics Information questions

A few sample questions with worked answers. Our free Electronics Information practice set has 207 questions in total — every one with a full explanation.

1. Which symbol represents a fuse?
A ✓
B
C
D
Why: A fuse is often drawn as a rectangle (or an oval) with a line through it — it breaks the circuit on overload.
2. What is the current through the resistor?
6V R = 3Ω I = ?
  • A.3 A
  • B.9 A
  • C.18 A
  • D.2 A ✓
Why: I = 6 ÷ 3 = 2 A.
3. A coil of wire that stores energy in a magnetic field when current passes through it is a(n)
  • A.resistor
  • B.capacitor
  • C.inductor ✓
  • D.diode
Why: An inductor stores energy in a magnetic field and opposes changes in current; it is rated in henries.
4. Which component stores electrical charge?
A ✓
B
C
D
Why: A capacitor (two parallel plates) stores charge in its electric field.
5. Which device protects a circuit by melting and breaking the connection when the current is too high?
  • A.Resistor
  • B.Battery
  • C.Switch
  • D.Fuse ✓
Why: A fuse contains a thin wire that melts on overcurrent, opening the circuit for protection.
Practise all 207 free

Electronics Information cheat sheet

The formulas and facts worth memorising for this subtest. See all ASVAB cheat sheets →

Laws
  • Ohm's law: V = I × R (I = V ÷ R, R = V ÷ I)
  • Power: P = V × I = I²R = V²/R
Circuits
  • Series: resistances ADD; current is the same everywhere
  • Parallel: voltage is the same across branches; two resistors R = product ÷ sum; total R drops
Know these
  • Units: volt (V), amp (A), ohm (Ω), watt (W), farad (F), hertz (Hz)
  • Resistor limits current · capacitor stores charge · diode = one-way · transistor = switch/amplify · transformer changes AC voltage · fuse protects
  • Conductor (copper) vs insulator (rubber/glass) vs semiconductor (silicon)
  • AC = alternating current · DC = direct current · an ohmmeter measures resistance

Other ASVAB subtest guides

Arithmetic Reasoning (AR)Mathematics Knowledge (MK)Word Knowledge (WK)Paragraph Comprehension (PC)General Science (GS)Auto Information (AI)Shop Information (SI)Mechanical Comprehension (MC)Assembling Objects (AO)