Current Electricity
Class 12 · Current Electricity

V–I Characteristics

Compare ohmic (linear), diode (exponential), bulb (super-linear) curves.

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Key Notes

01

Ohmic device: V-I straight line through origin, slope = R.

02

Diode: exponential I = Is(e^(V/V_T) − 1) — non-linear, asymmetric in V sign.

03

Bulb filament: super-linear (R rises with T) — concave V-I curve.

Formulas

Diode

V_T ≈ 26 mV at room temperature.

Important Points

Slope of V-I curve gives differential resistance dV/dI.

JEE often asks to identify device type from a V-I graph.

V–I Characteristics 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.