Current Electricity
Class 12 · Current Electricity

Power — 3 Forms

P = VI = I²R = V²/R. Three bars stay equal as you change V, R.

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Key Notes

01

All three forms equal: P = VI = I²R = V²/R. Pick the most convenient based on what's given.

02

Power consumed × time = energy used (kWh on the meter).

03

Bulbs rated by P at rated V — you can compute R = V²/P.

Formulas

Power forms

Use Ohm's law to switch between.

Important Points

100 W bulb at 220 V: I = P/V = 0.45 A; R = V²/P = 484 Ω (when hot).

P scales as V² for ohmic loads — small voltage drop gives big power loss.

Power — 3 Forms notes from sciphylab (also known as SciPhy, SciPhy Lab, SciPhy Labs, Physics Lab). Class 12 physics revision for JEE Mains, JEE Advanced, NEET UG, AP Physics 1/2/C, SAT, and CUET-UG.