What is Ohm's Law?

• A. V = IR
• B. I = V / R
• C. P = VI
• D. E = mc^2

Answer: (A)

Ohm's Law shows how voltage, current, and resistance fit together in a circuit. The main relationship is that the voltage across a resistor equals the current through it times its resistance: V = IR. This tells you that current scales with voltage and is limited by resistance, since higher resistance makes it harder for current to flow.

Units line up nicely: volts are volts (V), current in amperes (A), and resistance in ohms (Ω). One ohm is defined as one volt per ampere, so V = IR is dimensionally consistent.

If you know the voltage and resistance, you can find the current with I = V/R, which is just the same law solved for I. For example, with 12 V across a 4 Ω resistor, I = 12/4 = 3 A, and V = IR gives 12 = 3 × 4, confirming the relationship.

Other option expressions aren’t the fundamental form but are related: I = V/R is a rearrangement of the same law to solve for current; P = VI uses voltage and current to calculate power, not the direct V–I–R relationship; E = mc^2 is from a completely different domain (relativity).