What is Ohm's law expressed as an equation?

• A. I = VR
• B. V = IR
• C. V = RI
• D. R = VI

Answer: (B)

Voltage, current, and resistance are linked by Ohm's law: the voltage across a conductor equals the current through it times its resistance. This is why the equation V = IR expresses Ohm's law. The units line up neatly: volts equal amperes times ohms.

If you raise the current while keeping resistance the same, the voltage rises in proportion. If you raise the resistance while keeping the current the same, the voltage also rises proportionally. This reflects how a larger resistance makes it harder for current to flow, so more voltage is needed to push the same amount of current.

One form would imply current equals voltage times resistance, which doesn’t match the units of current. The form V = RI is mathematically the same as V = IR (multiplication is commutative), but the conventional way to present Ohm’s law is V = IR.