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ASVAB Practice Test · Electronics Information

ASVAB Practice Test: Electricity and Circuits Concepts

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Written by AI. Only units that passed a separate AI check (re-reading facts and numbers) are published. Tell us if you find a mistake.

Overview

This chapter covers how electricity works and how circuits are built. You will review current, voltage, and resistance, Ohm's law and power, series and parallel circuits, and common parts such as resistors, fuses, and switches.

Current is the flow of electric charge and is measured in amperes. Voltage is the push that moves the current and is measured in volts. Resistance slows the current and is measured in ohms. Ohm's law ties them together: voltage equals current times resistance. Power, measured in watts, equals voltage times current.

In a series circuit, parts are connected in one path, so the same current flows through each part and the resistances add up. If one part breaks, the whole circuit stops. In a parallel circuit, each part has its own branch, so each branch gets the full voltage and the others keep working if one fails.

Conductors, such as copper, let current flow easily, while insulators, such as rubber and plastic, block it. A fuse or circuit breaker opens the circuit when too much current flows, which protects the wiring. Direct current flows one way, like from a battery, and alternating current changes direction, like household power.

Key concepts

  • Current, voltage, resistance

    Current (amperes, A) is the flow of charge. Voltage (volts, V) is the push. Resistance (ohms) opposes the flow.

    Memory tipThink of water: voltage is pressure, current is flow.

  • Ohm's law

    V = I x R. Voltage equals current times resistance. Example: 2 amperes through 6 ohms needs 12 volts.

    Memory tipCover the one you want: I = V / R, R = V / I.

  • Electric power

    P = V x I. Power in watts equals voltage times current. Example: 120 volts x 2 amperes = 240 watts.

    Memory tipWatts = volts x amps.

  • Series circuit

    Parts are connected in a single path. The same current goes through each part, and total resistance is the sum of all resistances. One break stops everything.

    Memory tipSeries = single path.

  • Parallel circuit

    Each part is on its own branch. Every branch gets the same voltage. Adding branches lowers total resistance, and one failed branch does not stop the others.

    Memory tipHouse outlets are wired in parallel.

  • Fuse and circuit breaker

    Safety devices that open the circuit when too much current flows. A fuse melts and must be replaced; a breaker trips and can be reset.

    Memory tipBoth protect against overload.

  • AC and DC

    Direct current (DC) flows in one direction, as from a battery. Alternating current (AC) changes direction back and forth, as in household outlets.

    Memory tipBattery = DC, wall outlet = AC.

Often tested

  • Ohm's law: V = I x R.
  • Power: P = V x I.
  • Resistances in series add up.
  • Each parallel branch gets the full voltage.
  • Copper is a good conductor; rubber is an insulator.

Easy to confuse: Series vs. parallel circuits

FeatureSeriesParallel
Paths for currentOneMore than one
Same in every partCurrentVoltage
Total resistanceSum of all partsLess than the smallest part
If one part failsAll stopOthers keep working

3 sample questions

Verified practice questions from this unit.

Practice questionReviewedElectronics Information › Electricity and Circuits★★★★☆

Question 1. What is the unit used to measure electrical resistance?

  1. ① Volt
  2. ② Watt
  3. ③ Ampere
  4. ④ Ohm
▼ Show answer and explanation▲ Hide answer and explanation

Answer: ④ Ohm

Key point: Resistance is measured in ohms

Resistance is how much a part holds back the flow of electric current. It is measured in ohms, shown by the Greek letter omega.

Wrong choices

  • (A) Volt: The volt measures voltage, the electrical push.
  • (B) Watt: The watt measures power, the rate of using energy.
  • (C) Ampere: The ampere (amp) measures current, the flow of charge.
Practice questionReviewedElectronics Information › Electricity and Circuits★★★★☆

Question 2. A 12-volt battery is connected to a 4-ohm resistor. How much current flows through the resistor?

  1. ① 0.33 ampere
  2. ② 3 amperes
  3. ③ 48 amperes
  4. ④ 16 amperes
▼ Show answer and explanation▲ Hide answer and explanation

Answer: ② 3 amperes

Key point: Ohm's law: I = V / R

Ohm's law says V = I x R. To find current, divide voltage by resistance.

  1. I = V / R
  2. I = 12 V / 4 ohms = 3 A
  3. Check: 3 A x 4 ohms = 12 V. Correct.

Wrong choices

  • (A) 0.33 ampere: 0.33 comes from dividing 4 by 12, which is upside down.
  • (C) 48 amperes: 48 comes from multiplying 12 x 4. Ohm's law divides voltage by resistance to get current.
  • (D) 16 amperes: 16 comes from adding 12 + 4. Ohm's law does not add the numbers.
Practice questionReviewedElectronics Information › Electricity and Circuits★★★★☆

Question 3. A heater runs on 120 volts and draws 2 amperes. How much power does it use?

  1. ① 240 watts
  2. ② 60 watts
  3. ③ 118 watts
  4. ④ 122 watts
▼ Show answer and explanation▲ Hide answer and explanation

Answer: ① 240 watts

Key point: Power: P = V x I

Electric power equals voltage times current.

  1. P = V x I
  2. P = 120 V x 2 A = 240 W
  3. Check: 240 W / 120 V = 2 A. Correct.

Wrong choices

  • (B) 60 watts: 60 comes from dividing 120 by 2. Power multiplies voltage and current.
  • (C) 118 watts: 118 comes from subtracting 2 from 120.
  • (D) 122 watts: 122 comes from adding 120 + 2.
Practice 5 questions from this unit →