Talk:Electronics/DC Voltage and Current

KVL analogies
From the article:


 * Kirchoff's laws can be described with a sentence as "What comes in, must go out". It's that simple.

Not really. KCL works for "what goes in comes out", but KVL is more like "what goes up comes down", but not really. - Omegatron


 * Yes really: Voltage is exactly analagous to height in a gravitational situation.


 * Yeah, but it's not an exact analogy to KVL, is it? KVL is more like "if you go up 5 stairs and go down some stairs and are on the ground, you must have gone down 5 stairs."


 * Here is a better description of it:


 * "Applying KVL is analogous to taking a walk while paying attention to increases and decreases in altitude. If you walk in a loop (ie. you end your walk where you started) the net change in altitude is zero.  This is true for any path that you take for your walk. " - Omegatron 18:28, 2 Jul 2004 (UTC)

I agree, but maybe we could make it even simpler:
 * Kirchoff's laws can be described in 2 sentences: "What comes in, must go out". "What goes up, must come down". It's that simple.

I like the way those sentences hint that the KVL is not *always* true. (because we know "what goes up, must come down" is also not *always* true).

In a very few situations, I need the full equation:

sum( forces on a block of wood ) = mass * change in velocity / time

sum( voltages around a loop ) = area of loop * change in magnetic field / time

In most circuits the magnetic field does not change significantly. In most buildings, bridges, dams, etc., the velocity does not change significantly.

For practical circuit design, I generally assume that

sum( voltages around a loop ) = 0 (not exactly true, but close enough for circuit design)

in the same way that when I design a truss, I generally assume that

sum( forces on a block of wood ) = 0 (not exactly true, but close enough for bridge design).

-- DavidCary 14:17, 3 Jul 2004 (UTC)

Removed from article
In parallel voltage...


 * you can't have ideal voltage sources in parallel, if this is what is meant by this statement. it is equivalent to saying 3=5.  With source impedances, like real cells, they can be in parallel, but that would be silly...

The flow a circuit is that of a potential drop.


 * what??

de-emphasize current divider?
Voltage dividers are important to know. The idea of a voltage divider equation is used in many different circuits -- bandpass filters, power loss in power lines, etc. Is the current divider really that important? What is it used for? If it's not that important, perhaps we could de-emphasize it. Make it a "study problem" to practice Ohm's law? (or perhaps Thevenin or Norton equivalent circuits)? --DavidCary 04:09, 28 Jun 2005 (UTC)


 * I agree that voltage dividers are more often used. But this does not mean that current dividers are unimportant in electronic circuit analysis involving current sources it is easier to use current divider than voltage divider.  Currently I would say that voltage dividers are already more emphasised than current dividers.  I am not aware of any practical use of it.  The only use I can think of is if you wanted to have two different currents flowing in two different branches of the circuit.  But it is a useful in circuit analysis especially when there are current sources instead of voltage sources. --IKnowNothing 18:46, 28 Jun 2005 (UTC)