Enter any two of voltage, current and resistance to get the third from V = IR, together with the power dissipated.
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From the article Ohm's Law and Electrical Power — V, I, R and P Connected.
Question: A 4 Ω resistor is connected across a 12 V battery. Find the current and the power dissipated.
Current: I = V / R = 12 / 4 = 3 A
Power, using P = VI: P = (12)(3) = 36 W
Check with the other two forms:
P = I²R = (3)²(4) = (9)(4) = 36 W ✔
P = V²/R = (12)² / 4 = 144 / 4 = 36 W ✔
All three agree, as they must. In an exam, doing one and checking with a second costs about ten seconds and catches most arithmetic slips.
Worked in full in Ohm's Law and Electrical Power — V, I, R and P Connected.
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