Ohm’s law: see the circuit, solve the question
Work through a 24 V circuit, change voltage and resistance, and check your answer with units.
Name the unknown
Write down what the question asks before looking at the answer choices. Current is I, measured in amperes (A). Voltage is V, measured in volts (V). Resistance is R, measured in ohms (Ω).
Choose the relationship
For this ideal resistive DC example, use V = I × R. Rearrange to isolate the unknown. To find current, divide voltage by resistance.
Check the scale
Hold resistance constant: doubling voltage doubles current. Hold voltage constant: doubling resistance halves current. Use the circuit below to try both changes.
Answer in the requested unit
Convert only after solving in consistent units. The prefix milli means one thousandth, so multiply amperes by 1,000 to express milliamperes.
Change one thing.
Keep one slider fixed and move the other. Predict whether the current will rise or fall before reading the result.
That is 500 mA.
Take this into your next practice session
Write the known values and units, rearrange the formula, substitute, then check the size of the result. This example models an ideal resistor; it is not an AC impedance or appliance sizing calculation.
References and authorship
Original examples and study notes by CodeSafe Canada. Updated September 12, 2026.