What is Ohm's Law and how does it apply to a DC resistor?

• A. V = I R; current equals voltage divided by resistance; P = V I = I^2 R = V^2 / R.
• B. V = I R; current does not depend on resistance.
• C. P = V I / R; power is voltage times current divided by resistance.
• D. R = V / I; resistance is voltage divided by current.

Answer: (A)

Ohm’s Law describes a direct relationship between voltage, current, and resistance for a component that follows linear, ohmic behavior. For a DC resistor with a constant resistance, the current is I = V / R, meaning voltage and current scale together in proportion to the resistance. The power the resistor dissipates as heat is found from P = V I, which can be written as P = I^2 R or P = V^2 / R. This set of relationships—V = I R, I = V / R, and the power forms—tells you exactly how a DC resistor responds to applied voltage.

That’s why the best answer is the one that includes V = I R, the expression for current I = V / R, and the appropriate power formulas. The other statements either ignore how current depends on resistance, misuse the power relationship, or only give a rearranged form without presenting the full, useful set of relationships for a DC resistor.