Grade 9 Electricity Practice Exam 2026 – Your All-in-One Guide to Mastering Electricity Concepts!

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Which of the following equals electrical power for a resistor with current I and resistance R?

P = V × I

P = V^2 ÷ R

P = I × R

P = I^2 × R

Power in a resistor comes from how current and voltage relate. For a resistor, P = VI. Using Ohm’s law V = IR, you can substitute into that to get P = I(IR) = I^2R. So the form that uses only the current and the resistance is P = I^2 × R. The other expressions require knowing voltage (P = VI or P = V^2/R), or they would give a voltage (I × R) rather than power, so they don’t fit when you’re given I and R alone.