When Jeff Feddersen showed our class a demonstration of power generation, I was impressed by the visible effects of Lenz’s law when an electrical load was placed on the hand-cranked generator.

” Lenz’s law states that the current induced in a circuit due to a change in the magnetic field is so directed as to oppose the change in flux or to exert a mechanical force opposing the motion.” – Heinrich Lenz, 1834

We are surrounded by this effect – and the work that it does.

The past week I have reading and visualizing about the physics and models of magnetic waves, induction, electro-magnetic fields (EMF), magnetic moments, which brought me to Lenz’s law.
The subject is complex and filled with calculus the nuances of which are difficult to comprehend.
Looking at the “Cliff Notes” version, the concept is straight forward:

Field energy

The electric field stores energy. The energy density of the electric field is given by:

In general the incremental amount of work per unit volume δW needed to cause a small change of magnetic field δB is:

Conservation of momentum

Momentum must be conserved in the process, so if q_1 is pushed in one direction, then q_2 ought to be pushed in the other direction by the same force at the same time. However, the situation becomes more complicated when the finite speed of electromagnetic wave propagation is introduced (see retarded potential). This means that for a brief period of time, the total momentum of the two charges is not conserved, implying that the difference should be accounted for by momentum in the fields … Maxwell called this the “electromagnetic momentum” … Wikipedia .

Since taking apart my first motor to pull out the magnets when I was a child, to looking at motors today, every model that I have ever seen – in person or on paper – has either the magnet or the coil as a stationary object.

What if the magnetic resistance due to induction was allowed to self-optimize/be reduced within a given system? Aside from conserving momentum, would EMF be reduced, stay the same, or increase?

I’m thinking that I would like to design, construct, and analyze, an experiment and its outcome.

Peter Terezakis
ITP
Tisch School of the Arts
http://www.terezakis.com

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