Electronics Information — ASVAB practice questions

Three 6-Ω resistors in parallel have a total resistance of:

1. 2 Ω
2. 6 Ω
3. 12 Ω
4. 18 Ω

Answer: A — 2 Ω

Parallel: 1/R = 3/6 → R = 2 Ω. A) Correct. B) Single resistor. C/D) Series confusion.

A capacitor primarily stores energy in:

1. A magnetic field
2. An electric field
3. Heat
4. Sound

Answer: B — An electric field

A) That's an inductor. B) Capacitors store energy in an electric field between plates. C/D) Not energy storage modes here.

Ohm's Law is:

1. V = IR
2. P = IV
3. F = ma
4. E = mc²

Answer: A — V = IR

A) Correct — Ohm's Law: voltage = current × resistance. B) That's power (P = IV). C) Newton's 2nd law. D) Einstein's mass-energy.

A 12-volt source is connected across a single 4-ohm resistor. The current in the circuit is which of the following?

1. 0.33 amperes, since current falls as voltage divides
2. 48 amperes, found by multiplying volts times ohms
3. 8 amperes, the difference between volts and ohms
4. 3 amperes, found by dividing volts by resistance

Answer: D — 3 amperes, found by dividing volts by resistance

D) Correct — Ohm's law gives I = V/R = 12/4 = 3 amperes. A) tempts because it is the reciprocal, R divided by V. B) tempts by multiplying instead of dividing, which yields power-style arithmetic, not current. C) tempts by subtracting the two numbers, which has no basis in the law.

In a series circuit, the current through each component is:

1. Different for each
2. Equal to the voltage
3. Zero
4. The same throughout

Answer: D — The same throughout

A) That's parallel for voltage. D) Series shares current. C) Wrong. B) Mixes units.

The schematic symbol of two parallel lines (one shorter, broken) represents a:

1. Battery
2. Resistor
3. Capacitor
4. Inductor

Answer: A — Battery

A) Battery cells are drawn as long/short parallel lines. B) Resistor is a zigzag or rectangle. C) Capacitor uses two equal straight lines. D) Inductor uses coils.

AC differs from DC in that:

1. AC flows in one direction; DC alternates
2. Both are unidirectional
3. Both alternate
4. DC flows in one direction; AC alternates

Answer: D — DC flows in one direction; AC alternates

A) Reversed. D) DC is unidirectional; AC alternates. C/B) Wrong.

Resistance is measured in:

1. Amperes
2. Volts
3. Ohms
4. Watts

Answer: C — Ohms

A) Current. B) Voltage. C) Resistance. D) Power.

A component that stores energy in an electric field and opposes sudden changes in voltage is which of the following?

1. A resistor, which limits current and dissipates heat
2. A capacitor, which stores charge on facing plates
3. A diode, which allows current in one direction only
4. A transformer, which steps voltage up or down in AC

Answer: B — A capacitor, which stores charge on facing plates

B) Correct — a capacitor stores charge on plates separated by a dielectric, so voltage across it cannot jump instantly. A) tempts because resistors are the most familiar passive part, but they dissipate rather than store. C) tempts as a common part, yet a diode's job is one-way conduction. D) tempts because transformers also handle energy, but they couple AC magnetically.

DC current means:

1. The current alternates direction
2. The current flows in only one direction
3. The current is variable
4. The current is zero

Answer: B — The current flows in only one direction

A) That's AC. B) Correct — DC = direct current; one-direction flow, like a battery. C) Both AC and DC can be variable. D) DC can have any non-zero value.

What do a resistor, a capacitor, and an inductor each do in a circuit?

A resistor opposes current and dissipates energy as heat • a capacitor stores energy in an electric field and blocks DC • an inductor stores energy in a magnetic field and opposes changes in current.

Unit of current?

Ampere (amp, A).

Ohm's Law?

V = IR. Voltage = current × resistance.

In a series circuit and in a parallel circuit, what stays the same across all components?

Series: current is the same everywhere and voltage divides among components. • Parallel: voltage is the same across every branch and current divides.