Which equation expresses Ohm's law relating voltage, current, and resistance in a DC circuit?

• A. P = V × I
• B. V = I + R
• C. V = I × R
• D. I = V × R

Answer: (C)

Ohm's law for a DC circuit shows that the voltage across a conductor equals the current through it times its resistance. This relationship is written as V = IR, and it means that if you know how much current is flowing and the resistance the current meets, you can determine the voltage required (or the voltage will determine the current for a given resistance). The units line up as volts = amperes × ohms, which helps confirm the connection. The other formulas point to different ideas: P = VI describes electrical power, not the direct voltage–current–resistance link; V = I + R mixes quantities that aren’t added in this context; I = V × R would give incorrect results because current should scale with voltage divided by resistance (I = V/R). So the equation V = IR is the appropriate expression relating voltage, current, and resistance in a DC circuit.