06Class 12 Physics

Electromagnetic Induction formulas

Flux, Faraday's law and inductance formulas for Electromagnetic Induction. Lenz's law gives you the direction, and Faraday's law the size.

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All Physics formulas

Induced EMF

Magnetic flux: $\displaystyle \Phi = \vec B\cdot\vec A = BA\cos\theta$
Faraday's law: $\displaystyle \varepsilon = -N\frac{d\Phi}{dt}$
The minus sign is Lenz's law.
Motional EMF: $\displaystyle \varepsilon = Blv$
Rotating coil: $\displaystyle \varepsilon = NBA\omega\sin\omega t$

Inductance

Self-inductance: $\displaystyle \Phi = LI, \quad \varepsilon = -L\frac{dI}{dt}$
Long solenoid: $\displaystyle L = \mu_0 n^2 Al$
Mutual inductance: $\displaystyle \Phi_2 = MI_1, \quad \varepsilon_2 = -M\frac{dI_1}{dt}$
Energy in an inductor: $\displaystyle U = \tfrac12 LI^2$

Where students slip up

Forgetting EMF needs a change in flux. A large steady field through a still coil induces nothing.
Using the wrong direction with Lenz's law. The induced current opposes the change, not the field itself.
Using Blv when v isn't perpendicular to both l and B.

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