Undergrad Can a Core-less Dynamo Really Achieve Double Efficiency?

[goran d]

It seems that a core-less dynamo would have a maximum efficiency of 2.
The argument is as follows:
JxB emf= E.J emf
JxB does no work
E.J does work
Thus output is twice the mechanical energy spent
Inward Poynting vector?

 

[Dale]

The argument is as follows:
JxB emf= E.J emf

The left hand side is a vector. The right hand side is a scalar. That should be a good hint that the argument is wrong. (In case non conservation of energy weren’t enough of a hint)

 

[Baluncore]

Inward Poynting vector?

If you want to convert rotor energy to EM energy, you will need Poynting to flow outwards. Inward suggests it is actually a motor or resistor that consumes electrical energy.

 

[berkeman]

It seems that a core-less dynamo would have a maximum efficiency of 2.
The argument is as follows:
JxB emf= E.J emf
JxB does no work
E.J does work
Thus output is twice the mechanical energy spent
Inward Poynting vector?

We do not allow the discussion of nonsense like over-unity processes (efficiency = 2). Per the PF rules:

Pseudoscience, such as (but not limited to):
Perpetual motion and "free energy" discussions (see our Insights Article here)
http://en.wikipedia.org/wiki/Perpetual_motion
http://www.skepdic.com/freeenergy.html
http://www.skepdic.com/perpetual.html

You are on a 10-day vacation from the PF now. Not that it seems to matter -- you seem to only stop by PF every year or two to post nonsense. If you do it again, you will be permanently banned. Have a nice day.