P = IV Formula – Electric Power Practice
P = IV — Also P = I²R and P = V²/R
Electrical power is P = IV. Equivalent forms are P = I²R and P = V²/R when resistance is known.
Guide — how to use this formula
- 1. Pick P = IV, I²R, or V²/R from the knowns.
- 2. I = P/V; R = P/I² or R = V²/P.
- 3. Energy transferred: E = Pt.
- 4. 1 kW = 1000 W.
Derivation
From energy transfer and Ohm’s law:
- Power as voltage × current:
P = IV - With V = IR:
P = I^{2}R = \frac{V^{2}}{R}
Convert mA → A before P = IV.
Examples
Example: 12 V, 2 A
P = 24 W.
Example: I²R
I = 2 A, R = 5 Ω → P = 20 W.