Which law is described by the equation V = I × R?

• A. Ohm's Law
• B. Kirchhoff's Law
• C. Faraday's Law
• D. Coulomb's Law

Answer: (A)

This equation shows how voltage, current, and resistance relate in a conductor, capturing a direct proportionality between them. When resistance stays constant, the current through a component scales linearly with the applied voltage, with resistance acting as the constant of proportionality. In other words, the voltage across a resistor equals the current through it times its resistance, so knowing any two of the quantities lets you find the third. This is the essence of Ohm’s law and is especially true for ohmic devices like many metal resistors at a steady temperature.

Voltage, current, and resistance have clear meanings: voltage is the driving potential, current is the flow of charge, and resistance is how much the material resists that flow. The units fit neatly: volts equal amperes times ohms (V = A × Ω). While this relationship is fundamental for many circuits, some components don’t follow it exactly (nonlinear devices or conditions where resistance changes with temperature), so V = IR is most accurate for devices that behave linearly.

Other laws describe different ideas: Kirchhoff’s laws deal with the sum of voltages around loops or currents at nodes, not the direct V = IR relationship; Faraday’s law concerns induced voltage from changing magnetic fields; Coulomb’s law describes the force between electric charges.