Which statement correctly expresses power using resistance only?

• A. P = VI
• B. P = I^2 R
• C. P = V^2 / R
• D. P = R / V

Answer: (B)

Power dissipated in a resistor can be written using resistance with the current by applying Ohm’s law to the basic formula P = VI. Since V = IR, substitute into P = VI to get P = I(IR) = I^2 R. This shows power depends on the current squared and the resistance, which is why this form is correct when you’re expressing power with resistance in the picture.

Intuitively, if you double the current through a given resistor, the power (and heat) becomes four times, because it scales with I^2. The form using P = V^2 / R or P = VI uses voltage rather than current, so they don’t express “power using resistance” in the same way. And P = R / V isn’t a valid way to get watts, since its units don’t come out as power.