Which equation expresses Ohm's Law for a resistor?

Which equation expresses Ohm's Law for a resistor?

• A. V = I / R
• B. V = I × R
• C. I = V × R
• D. R = V × I

Answer: (B)

Ohm's Law for a resistor ties together voltage, current, and resistance in a simple linear relationship: the voltage across the resistor equals the current through it times its resistance. This is why the correct expression is V = I × R. It shows that if you know the current and the resistance, you can find the voltage, and if you know the voltage and resistance, you can find the current (I = V / R). The units line up neatly too: volts equal amperes times ohms, since 1 Ω = 1 V/A, giving V = A × (V/A) = V. The other forms aren’t consistent with how a resistor behaves: V = I / R would imply voltage shrinks as resistance grows, I = V × R would give current in the wrong proportion and units, and R = V × I would imply resistance is the product of voltage and current, which doesn’t match the defined unit relationship.

Ohm's Law for a resistor ties together voltage, current, and resistance in a simple linear relationship: the voltage across the resistor equals the current through it times its resistance. This is why the correct expression is V = I × R. It shows that if you know the current and the resistance, you can find the voltage, and if you know the voltage and resistance, you can find the current (I = V / R). The units line up neatly too: volts equal amperes times ohms, since 1 Ω = 1 V/A, giving V = A × (V/A) = V. The other forms aren’t consistent with how a resistor behaves: V = I / R would imply voltage shrinks as resistance grows, I = V × R would give current in the wrong proportion and units, and R = V × I would imply resistance is the product of voltage and current, which doesn’t match the defined unit relationship.