Which equation expresses Ohm's Law?

• A. P = V I
• B. I = V + R
• C. V = I R
• D. R = V - I

Answer: (C)

Ohm’s Law describes how voltage, current, and resistance relate to each other, with voltage being the product of current and resistance. This direct relationship is captured by V = IR, so the expression that matches this fundamental connection is the correct one. It shows how increasing current or resistance changes the voltage across a conductor.

The other forms don’t fit the basic relationship. I = V + R would add voltage and resistance, which doesn’t describe how current behaves. R = V - I would subtract current from voltage, which also doesn’t align with the units or the physics. P = VI represents electrical power, not the basic voltage–current–resistance link (though power can be derived from Ohm’s Law as P = I^2R or P = V^2/R). You can, of course, rearrange V = IR to I = V/R or R = V/I if you need a different variable, but the direct Ohm’s Law expression is V = IR.