Hi,
I have been reading around about back EMF and their derivations for simple DC motors. However for some reason, the step between obtaining the total emf of the motor from summing the individual emf of the coils is not very clear. For example:
Induced emf due to single coil: e = d∅_c/dt...
Thanks for the very speedy reply =).
I see. Unfortunately, we have yet to cover Stoke's Theorem and curls until next year (which is the 2nd year in undergraduate electrical engineering).
Your reply links in with explanation on this forum (which hopefully will make more sense by next...
Hello Reader,
Basically in Faraday's law, a change of flux over time induces an EMF. I was wondering why is it the enclosed magnetic flux and NOT the magnetic flux through the conductor that we consider.
More specifically, I understand that the flux through a rectangular surface would be...
Well, the idea in mind that I have is that holes travel in the opposite direction of electrons therefore they follow the path of conventional current. I know I am assuming and treating holes as an existing positive charged particle; is that the reason why the hole current density expression...
With that piece of information, it makes a lot of sense. The only thing that bothers me then though is the other definition of mobility which is, μ = |Drift Velocity| ÷ |E|, hence that would imply that enμE , epμE > 0 thus positive. However, aren't holes 'traveling' the opposite direction of...
Good Morning,
The equations under investigation:
Electrons: J = enμE + eD(dn/dx)
Holes: J = epμE - eD(dp/dx)
n or p = concentration of electrons or holes respectively
D = diffusion constant
μ = mobility
The question in mind is as follows:
If holes are...
Oh I see. The Trigonometry method is a linear approximation that does not take into account of the larger angles where the approximation deviates from this linearity. That explains the difference in answers .
Thanks for clearing that up :smile:
Thanks for the reply. That is what I thought, although I tried to improve this approximation by using the formula that takes into account bigger amplitudes: http://upload.wikimedia.org/wikipedia/en/math/3/0/1/3014cdccf9d3df9770a001b84ae6ac80.png
However, the percentage error difference...
1. The Question from Text:
"A forest playground has a tyre hanging from a tree branch. The tyre behaves like a pendulum, with a rope of 4.0 metres length, and the tyres mass 15 kg. A child of mass 45 kg swings on the tyre by pulling it 3.0 metres to one side and leaping on. What is the maximum...
Short story:
How does one go about to derive x = a cos(wt)? The way it is derived in my book is from the "SHM Diagram" file that I have uploaded but it seems that the diagram is incorrect as it does not correspond to the expression. Also, why is the Amplitude in the expression constant when the...