Current Electricity
Class 12 · Current Electricity

Joule's Heating Law

H = I²Rt. Wire glows brighter at higher P. Live ΔT estimate.

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Key Notes

01

H = I²Rt — heat dissipated when current I flows through R for time t.

02

Equivalent forms: H = V²t/R = VIt.

03

Underlies heaters, fuses, filament bulbs, and explains why thin wires get hot.

Formulas

Joule's law

Heat in joules; t in seconds.

Important Points

Fuses melt because of localised heating — designed to fail safely.

Power-rated devices: don't exceed rated current or they overheat.

Joule's Heating Law 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.