Question

Lenz's law is based on conservation of

• A. charge
• B. mass
• C. energy
• D. momentum

Answer 1

The correct option is C energy

Lenz's law is a common way of understanding how electromagnetic circuits obey Newton's third law and the conservation of energy.

When an external force or energy causes motion of circuits involved or change of flux, an induced current with the induced field and the associated energy occurs to conserve the energy.

$ϵ=-L\frac{di}{dt}$

$ϵi=-L\frac{di}{dt}i=-\frac{L}{2}\frac{d{i}^2}{dt}=-\frac{d}{dt}\left(\frac{1}{2}L{i}^2\right)$

Above equation states the electromagnetic energy spent = $ϵi$ , is equal to the negative of rate of change of stored magnetic energy = $\frac{1}{2}L{i}^2$.