Coulombs I can do.
They quantify charge and are proportional to the number of electrons shifted, and not too difficult to visualise as electrons are real little round things.
In a circuit they are being pushed up a gradient against their natural tendency to stay still, if you get my meaning.
Coulombs get an outing in CΔV=IT, that particularly handy formula for sizing reservoir and de-coupling capacitors.
Now, I do occasionally wrestle with LΔI=VT when picking inductors for switching converters.
And I know this equation is equal to volt.seconds.
But the trouble starts if I have to visualise volt.seconds as they are far too abstract.
Can anybody help?
Alice (special contributor)
By the way, the title An Engineer in Wonderland was inspired by the 1967 book 'The Engineer in Wonderland' by Professor Eric Laithwaite: champion of the linear induction motor, and a man who certainly knew his volt.seconds.
(Picture - wackyvorlon, under Creative Commons Attribution Licence)
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Comments (4)
Hmmmmm !
Having just stuck my fingers across the terminals of a PP3 battery and counted 1-mississippi , I am still no further enlightened as to what a volt-second ( or 9 in my case ) is.
And I'm not sure I ever will be.
I think the root of the problem is the way you have grouped the terms of the equation.
When visualising inductor currents I always re-arrange the equation into the form ;
dI/dT=V/L
This to me makes much more sense.
The rate of rise of current throught the inductor dI/DT is equal to the applied voltage divided by the inductance value.
So 1 volt across a 1mH inductor gives 1000A/sec.
Easy :O)
Posted by John Barr | March 20, 2008 12:01 PM
Posted on March 20, 2008 12:01
Volt-seconds to me are like hitting a block to slide up a plank.... with friction. A steep ramp needs a lot of clout to get the block to the top... Height is equivalent to volts. a long ramp needs a lot of clout to get the block to the end - even if a gradual incline.... equivalent to a lot of seconds. So Volt-seconds are an impulse (not the sort in girl's aerosols). Make any sense? (I may be wrong, too!).
Posted by Ken Chicken | March 20, 2008 1:58 PM
Posted on March 20, 2008 13:58
It might help to realize that a volt*second is identically a Weber, and that Webers/meter^2 are Tesla. So volt*seconds are equivalent to magnetic lines. Remember that a changing magnetic field is the basis of induction? Well a Weber/second is a volt. In a standard setup, the change of a magnetic field of one weber per second induces one volt. And a volt is just a Joule per coulomb. So a weber per second field change acting on a coulomb of charge requires one joule of energy. I do not know if that helps any. But switch to magnetic units and concepts when you come to volt*seconds. Finally, a Weber is 10^8 lines of magnetic something. You can get some conversion (including volt*seconds) at http://online.unitconverterpro.com/conversion-tables/convert-group/factors.php?cat=magnetic-flux&unit=1&val=
Posted by Richard Collins | July 26, 2008 9:58 PM
Posted on July 26, 2008 21:58
Thanks Mr Collins.
All is clear.
'Alice'
Posted by Alice | July 30, 2008 2:22 PM
Posted on July 30, 2008 14:22