Ohm's law and basic circuit math show up all over the journeyman exam, and they're also the stuff you use every day on the job. If you can't do these fast, everything else takes longer.
These 15 problems cover Ohm's law, power, series and parallel circuits, and unit conversions. Grab a calculator.
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Question 1 of 15
A 1500-watt heater operates at 120 volts. What is the current draw?
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Answer: A. 12.5 A
I = 1500 ÷ 120 = 12.5 amperes.
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Question 2 of 15
A load draws 6 A at 120 V. What is the power in watts?
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Answer: A. 720 W
P = 120 × 6 = 720 W.
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Question 3 of 15
In a series circuit, the current through each component is:
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Answer: A. The same
In a series circuit, the same current flows through all components.
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Question 4 of 15
If a 120-volt circuit draws 20 amperes, what is the resistance?
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Answer: A. 6 Ω
R = 120 ÷ 20 = 6 ohms.
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Question 5 of 15
Convert 15,000 VA to kVA.
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Answer: A. 15 kVA
15,000 ÷ 1000 = 15 kVA.
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Question 6 of 15
Two resistors, 4 Ω and 6 Ω, are connected in parallel. What is the total resistance (rounded to one decimal)?
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Answer: A. 2.4 Ω
RT = (4×6)/(4+6) = 24/10 = 2.4 ohms.
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Question 7 of 15
Which formula correctly represents Ohm’s Law?
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Answer: A. V = I × R
Ohm’s Law states that voltage equals current multiplied by resistance (V = I × R).
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Question 8 of 15
Convert 0.0025 A to milliamps (mA).
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Answer: A. 2.5 mA
0.0025 × 1000 = 2.5 mA.
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Question 9 of 15
A 120 V series circuit uses two resistors: R1 = 5 Ω and R2 = 15 Ω. What is the voltage across R2?
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Answer: A. 90 V
In a series circuit, the same current flows through every resistor. First find total resistance: RT = 5 Ω + 15 Ω = 20 Ω. Then find current: I = 120 V ÷ 20 Ω = 6 A. Voltage across R2 is V = I × R = 6 A × 15 Ω = 90 V.
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Question 10 of 15
In a purely resistive circuit, if voltage doubles while resistance remains constant, what happens to current?
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Answer: A. It doubles
With resistance constant, current is directly proportional to voltage (I = V ÷ R). Doubling V doubles I.
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Question 11 of 15
A 1.2 kW load operates for 3 hours. How many kilowatt-hours (kWh) are used?
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Answer: A. 3.6 kWh
1.2 kW × 3 h = 3.6 kWh.
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Question 12 of 15
A 120 V source feeds two parallel resistors: 10 Ω and 20 Ω. What is the total current?
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Answer: A. 18 A
I1 = 120/10 = 12 A. I2 = 120/20 = 6 A. IT = 12 + 6 = 18 A.
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Question 13 of 15
If a 240-volt circuit supplies a load drawing 10 amperes, what is the power?
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Answer: A. 2400 W
Use Watt’s Law: power equals voltage times current. P = V × I, so P = 240 V × 10 A = 2400 W.
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Question 14 of 15
Convert 750 watts to kilowatts (kW).
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Answer: A. 0.75 kW
750 ÷ 1000 = 0.75 kW.
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Question 15 of 15
Two resistors, 4 Ω and 6 Ω, are connected in series. What is the total resistance?
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Answer: A. 10 Ω
RT = 4 + 6 = 10 ohms.
Want more? Electrician Practice has 1,100+ practice questions with explanations.
If series and parallel tripped you up, remember: series adds resistance, parallel splits current. Most mistakes come from mixing those up.
Practice until you can pick the right formula without thinking. That speed matters on a timed exam.
Want more questions like these?
Electrician Practice has 1,100+ practice questions with explanations, timed practice exams, and weak-area drills.