Ohm's Law is represented by which equation?

• A. Q = CV
• B. V = IR
• C. E = mgh
• D. P = IV

Answer: (B)

Ohm's Law describes how voltage, current, and resistance relate in a circuit: the voltage across a conductor equals the current through it times its resistance. This direct relation is written as V = IR. It shows that for a fixed resistance, increasing the voltage increases the current proportionally, and for a given voltage, increasing the resistance decreases the current. For example, with a 4-ohm resistor and 3 amperes flowing, the voltage across it is V = IR = 4 × 3 = 12 volts. This single equation lets you find any one quantity if you know the other two. The other formulas shown correspond to different concepts: Q = CV is for capacitors, E = mgh is gravitational potential energy, and P = IV describes power (which can be related to Ohm's Law but is not the basic relation for a resistor).