Power of electric current is given by P = V I.

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

Answer: (A)

Power is the rate at which energy is transferred in a circuit. This rate comes from the work done on charges as they move through a component, which depends on how much voltage pushes the charges (voltage) and how many charges are moving each second (current). Multiplying these gives the power: P = V × I, with the result in watts.

You can see other equal forms if you use Ohm’s law, V = IR. Substituting into P = VI gives P = I^2R, and substituting V = IR into P = VI also gives P = V^2 / R. These are just different ways to express the same power for a resistor or any element where V, I, and R are related by Ohm’s law.

The expression I × R is voltage, not power, so it does not represent power itself.

Example: a 5 V potential across a component with a 2 A current yields P = 5 × 2 = 10 watts.