What is Ohm's Law and how is it used in diagnosing bus electrical circuits?

• A. V = I × R; It predicts voltage, current, or resistance to locate faults and verify circuit behavior.
• B. P = V × I; It calculates power usage in the circuit.
• C. E = IR^2; It describes energy loss in resistors.
• D. Ohm's Law relates to the speed of electrons in a conductor.

Answer: (B)

Ohm's Law is the rule that links voltage, current, and resistance in an electrical path. The core relation is V = I × R, which lets you predict how much current will flow for a given voltage and resistance, or what voltage you should see if you know the current and resistance. In diagnosing bus electrical circuits, this is your go-to tool for spotting abnormal behavior. By measuring the supply voltage and the current drawn by a circuit or branch, you can calculate the expected resistance and compare it to spec. If the numbers don’t match, you can infer where a fault lies—such as a bad connection, corrosion, damaged wiring, or a faulty component causing an unexpected drop or limit in current.

Power, which is how much work the circuit can do, is P = V × I. This is derived from Ohm's Law and helps you estimate heat and energy usage, but it is not Ohm's Law itself. The other options aren’t the fundamental relationship: E = IR^2 isn’t a standard form, since the common forms are P = I^2R or P = V^2/R, and Ohm's Law is not about the speed of electrons.