In Ohm's Law, which expressions correctly relate voltage (V), current (I), and resistance (R)?

• A. V = IR
• B. I = V / R
• C. R = V / I
• D. All of the above

Answer: (D)

Ohm's Law ties voltage, current, and resistance together in a simple proportional relationship: voltage equals current times resistance. Because of this, you can algebraically rearrange to express any one variable in terms of the other two: current equals voltage divided by resistance, and resistance equals voltage divided by current. All three forms describe the same relationship, so each expression is correct. For example, with a 10-ohm resistor and 2 amperes of current, the voltage is V = IR = 10 × 2 = 20 V; equivalently, I = V/R = 20/10 = 2 A, and R = V/I = 20/2 = 10 Ω.