ASVAB Study – Free Practice Tests & Study Guides for 2025

The Electronics Information (EI) section of the ASVAB is designed to evaluate your understanding of electrical principles and systems. Whether you're aiming to become an avionics technician, electrician’s mate, or fire controlman, a strong grasp of basic circuit theory—including Ohm’s Law, current, voltage, and resistance—is essential.

Ohm’s Law and Basic Circuit Theory for the ASVAB: Master Electrical Questions with Confidence

In this in-depth guide, you'll learn the foundational electrical concepts tested on the ASVAB and gain the confidence to solve circuit-based problems like a pro.

 

Table of Contents

1. What Is Ohm’s Law?
2. Key Electrical Quantities: Voltage, Current, Resistance
3. Calculating with Ohm’s Law: V = I × R
4. Series vs. Parallel Circuits
5. Power in Electrical Circuits
6. Electrical Symbols and Diagrams
7. Conductors, Insulators, and Semiconductors
8. Capacitors and Inductors (Basic Overview)
9. Safety Precautions and Real-World Applications
10. Study Tips and Tricks
11. Practice Questions and Explanations
12. Conclusion

 

1. What Is Ohm’s Law?

Ohm’s Law is the cornerstone of basic electrical theory. It defines the relationship between voltage (V), current (I), and resistance (R) in an electrical circuit.

Formula:

V = I × R

Where:

• V = Voltage (Volts)
• I = Current (Amperes)
• R = Resistance (Ohms)

This formula can be rearranged to solve for any unknown:

• I = V ÷ R
• R = V ÷ I

 

2. Key Electrical Quantities

Voltage (V):

Also known as electric potential difference. It is the “pressure” that pushes electrons through a circuit.

Current (I):

The flow of electric charge, measured in amperes (A).

Resistance (R):

The opposition to the flow of current, measured in ohms (Ω).

⚡ Quick Tip for ASVAB:

Visualize voltage as water pressure, current as the flow of water, and resistance as the narrowness of the pipe.

 

3. Calculating with Ohm’s Law: V = I × R

Example 1:
A circuit has a resistance of 10 Ω and a current of 2 A. What is the voltage?

V = I × R = 2 × 10 = 20 volts

Example 2:
You have a 24-volt battery connected to a 6-ohm resistor. What is the current?

I = V ÷ R = 24 ÷ 6 = 4 A

 

4. Series vs. Parallel Circuits

Understanding how components are arranged affects current and voltage distribution.

Series Circuit:

• Current is the same through all components.
• Total resistance = sum of all resistors:
  Rₜ = R₁ + R₂ + R₃...

Parallel Circuit:

• Voltage is the same across all branches.
• Total resistance is less than the smallest resistor:
  1/Rₜ = 1/R₁ + 1/R₂ + 1/R₃...

✅ Common ASVAB Tip:

Series = current constant
Parallel = voltage constant

 

5. Power in Electrical Circuits

The power (P) consumed by a circuit can be calculated with:

P = V × I

Other useful forms using Ohm’s Law:

• P = I² × R
• P = V² ÷ R

Units: Power is measured in watts (W).

Example:
If a circuit has 2 amps of current and 12 volts:

P = 2 × 12 = 24 watts

 

6. Electrical Symbols and Diagrams

ASVAB test questions may include basic circuit diagrams. Here are common symbols:

Component	Symbol
Resistor	─//─
Battery	+| |-
Ground	⏚
Switch (open)	─o o─
Lamp/Bulb	(X)

You should be able to interpret these diagrams and apply Ohm’s Law accordingly.

 

7. Conductors, Insulators, and Semiconductors

Conductors:

Allow electricity to flow easily (e.g., copper, aluminum).

Insulators:

Resist electric flow (e.g., rubber, plastic, glass).

Semiconductors:

Materials that conduct under certain conditions (e.g., silicon, used in electronics).

 

8. Capacitors and Inductors (Basic Overview)

You may encounter basic mentions of these components:

Capacitors:

• Store electrical energy.
• Measured in farads (F).
• Used to smooth voltage or store charge.

Inductors:

• Oppose changes in current.
• Measured in henrys (H).
• Common in transformers and motors.

Don’t worry too much—basic understanding is sufficient for the ASVAB.

 

9. Safety Precautions and Real-World Applications

Electrical safety is critical in military jobs. You should:

• Never touch live wires.
• Use insulated tools.
• Be familiar with circuit breakers and fuses.

Real-World Military Roles:

• Aircraft electricians
• Radar technicians
• Missile system repair

Understanding voltage, current, and resistance helps diagnose and fix real systems.

 

10. Study Tips and Tricks

• Use triangle diagrams to memorize formulas:

 

   V

  ———

 I | R

• Practice flashcards: symbols, formulas, units
• Use apps like ASVAB Practice Test 2025 or Mometrix
• Watch YouTube videos with circuit animations

 

11. Practice Questions and Explanations

Question 1:

A circuit has 12 V and 3 A. What is the resistance?

A. 4 Ω
B. 36 Ω
C. 0.25 Ω
D. 15 Ω

✅ Correct Answer: A
Explanation: R = V ÷ I = 12 ÷ 3 = 4 Ω

 

Question 2:

Which material is the best conductor of electricity?

A. Rubber
B. Copper
C. Plastic
D. Glass

✅ Correct Answer: B
Explanation: Copper is a highly efficient conductor.

 

Question 3:

Which formula correctly represents Ohm’s Law?

A. V = R ÷ I
B. I = V × R
C. V = I × R
D. R = I × V

✅ Correct Answer: C
Explanation: Ohm’s Law is V = I × R.

 

Question 4:

In a parallel circuit, what remains constant across all components?

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

✅ Correct Answer: B
Explanation: Voltage is the same across each branch in a parallel circuit.

 

Question 5:

A 6-ohm resistor has a current of 2 A. What’s the voltage?

A. 12 V
B. 3 V
C. 0.33 V
D. 4 V

✅ Correct Answer: A
Explanation: V = I × R = 2 × 6 = 12 V

 

12. Conclusion

Understanding Ohm’s Law and the fundamentals of basic circuits gives you a major edge on the ASVAB. Whether you’re solving for voltage in a test question or preparing for a technical role in the military, these concepts will serve you well.

 Key Takeaways:

• Master the formula V = I × R
• Understand the difference between series and parallel circuits
• Be comfortable with power calculations and circuit symbols

Consistent practice, especially with diagrams and real-world examples, will sharpen your understanding and boost your score