ASVAB Practice Test · Electronics Information
Written by AI · Not yet reviewed by staffASVAB Practice Test Electricity and Circuits Summary
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- About 15 of 15 Electronics Information questions (100%)
Current, voltage, resistance, Ohm's law, series and parallel circuits, and common parts.
📖 See Electricity and Circuits concepts →Electricity and Circuits: must-know points
- Ohm's law: V = I x R.
- Power: P = V x I.
Electricity and Circuits: 10 sample questions
Question 1. What is the unit used to measure electrical resistance?
- ① Volt
- ② Watt
- ③ Ampere
- ④ Ohm
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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.
Question 2. A 12-volt battery is connected to a 4-ohm resistor. How much current flows through the resistor?
- ① 0.33 ampere
- ② 3 amperes
- ③ 48 amperes
- ④ 16 amperes
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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.
- I = V / R
- I = 12 V / 4 ohms = 3 A
- 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.
Question 3. A heater runs on 120 volts and draws 2 amperes. How much power does it use?
- ① 240 watts
- ② 60 watts
- ③ 118 watts
- ④ 122 watts
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Answer: ① 240 watts
Key point: Power: P = V x I
Electric power equals voltage times current.
- P = V x I
- P = 120 V x 2 A = 240 W
- 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.
Question 4. Three resistors of 10 ohms, 20 ohms, and 30 ohms are connected in series. What is the total resistance?
- ① 20 ohms
- ② 5.45 ohms
- ③ 60 ohms
- ④ 6,000 ohms
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Answer: ③ 60 ohms
Key point: Series resistors add up
In a series circuit, current passes through each resistor one after another, so the resistances add.
- Total = 10 + 20 + 30
- Total = 60 ohms
- Check: the total in series is always larger than the biggest single resistor (30). 60 is larger. Correct.
Wrong choices
- (A) 20 ohms: 20 ohms is the average of the three values, not the total.
- (B) 5.45 ohms: 5.45 ohms is the total if the three were connected in parallel, not series.
- (D) 6,000 ohms: 6,000 comes from multiplying the values; series resistances are added.
Question 5. Two 10-ohm resistors are connected in parallel. What is the total resistance?
- ① 10 ohms
- ② 100 ohms
- ③ 5 ohms
- ④ 20 ohms
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Answer: ③ 5 ohms
Key point: Equal resistors in parallel: R / number
When equal resistors are in parallel, divide one resistor's value by how many there are.
- Total = 10 ohms / 2 = 5 ohms
- Check with the product-over-sum rule: (10 x 10) / (10 + 10) = 100 / 20 = 5 ohms. Correct.
The total in parallel is always smaller than the smallest single resistor.
Wrong choices
- (A) 10 ohms: 10 ohms is the value of only one resistor; adding a parallel path lowers the total.
- (B) 100 ohms: 100 comes from multiplying 10 x 10 without dividing by the sum.
- (D) 20 ohms: 20 ohms is the total if they were connected in series.
Question 6. In a simple series circuit, what is true about the current?
- ① It is largest through the biggest resistor
- ② It splits up among the different branches
- ③ It is the same through every part of the circuit
- ④ It drops to zero after the first resistor
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Answer: ③ It is the same through every part of the circuit
Key point: Series circuit: same current everywhere
A series circuit has only one path. All the charge must pass through each part in turn, so the current is the same at every point. The voltage, however, is divided among the parts.
Wrong choices
- (A) It is largest through the biggest resistor: Current is the same everywhere in a series loop; the biggest resistor gets the largest voltage drop, not more current.
- (B) It splits up among the different branches: Splitting into branches happens in a parallel circuit, not a series circuit.
- (D) It drops to zero after the first resistor: If the current were zero after the first resistor, nothing would flow at all; the same current goes all the way around.
Question 7. Which of these materials is a good electrical insulator?
- ① Rubber
- ② Aluminum
- ③ Copper
- ④ Salt water
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Answer: ① Rubber
Key point: Insulators block current; metals conduct
An insulator is a material that does not let electric current flow easily. Rubber, plastic, glass, and dry wood are insulators. That is why wire is covered with rubber or plastic.
Wrong choices
- (B) Aluminum: Aluminum is a metal and conducts electricity well.
- (C) Copper: Copper is one of the best conductors; it is used in most wiring.
- (D) Salt water: Salt water conducts electricity because of the dissolved salt.
Question 8. Which electronic part stores electric charge between two plates separated by an insulator?
- ① Diode
- ② Fuse
- ③ Resistor
- ④ Capacitor
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Answer: ④ Capacitor
Key point: A capacitor stores electric charge
A capacitor has two metal plates with an insulator between them. It stores electric charge and can release it later. Its unit is the farad.
Wrong choices
- (A) Diode: A diode lets current flow in only one direction.
- (B) Fuse: A fuse protects a circuit by melting when current is too high.
- (C) Resistor: A resistor limits current; it does not store charge.
Question 9. What does a diode do in a circuit?
- ① Raises the voltage of the circuit
- ② Stores energy in a magnetic field
- ③ Lets current flow equally in both directions
- ④ Lets current flow in only one direction
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Answer: ④ Lets current flow in only one direction
Key point: A diode passes current one way only
A diode works like a one-way valve for electricity. Current flows easily in the forward direction and is blocked in the reverse direction. Diodes are used to change AC into DC.
Wrong choices
- (A) Raises the voltage of the circuit: A transformer can raise AC voltage; a diode does not.
- (B) Stores energy in a magnetic field: An inductor (coil) stores energy in a magnetic field.
- (C) Lets current flow equally in both directions: A plain wire or resistor passes current both ways; a diode blocks one direction.
Question 10. What type of current does a car battery supply?
- ① Alternating current (AC)
- ② Direct current (DC)
- ③ Three-phase alternating current
- ④ Current that changes direction 60 times a second
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Answer: ② Direct current (DC)
Key point: Batteries supply direct current (DC)
A battery pushes current in one direction only, from its negative side through the circuit to its positive side. This is direct current, or DC.
Wrong choices
- (A) Alternating current (AC): Alternating current changes direction back and forth; a battery's current flows one way.
- (C) Three-phase alternating current: Three-phase AC comes from power plants and large generators, not batteries.
- (D) Current that changes direction 60 times a second: Current that reverses 60 times a second describes U.S. household AC, not a battery.
Test yourself.