Michelin ECT Full Course Practice Exam

Power in a DC circuit is the rate at which energy is transferred, equal to the voltage across a component times the current through it: P = V × I. This form directly gives watts and applies universally in DC circuits. If you know resistance, you can rewrite it as P = I^2R or P = V^2/R via Ohm’s law, but the fundamental, universally applicable expression is P = V × I. The other forms shown are not general power formulas: I^2/R is not the standard expression (the correct resistor form is I^2R), V^2 is incomplete (you’d need division by R to get power), and IR gives voltage, not power.