# Electronics

• 06-01-2002, 01:22 PM
Ed Mack
Ok, I know the basics (volts, amps, various components, electrons flow out of -ve)

I started having a go at a little electronic sim, it's very simple right now with quite a few flaws like current doesn't split, it doesn't use relistic values but any way,

How in real life do the components only work when they are in a complete dircuit? I've found that programming things the way they do in real life usually works best.

(Oh, and here's my shoddy swf: http://ed.gamegeared.com/flash/circuit.swf )

Thanks!
• 06-01-2002, 11:14 PM
brutfood
Current only flows trough a component where there is a potential difference.

I think to write this sim, you need to know ohms law:-

V = I * R so I = V / R R = V / I

Going back to your original question, if you have an open circuit, Resistance (R) is infinate (not futile), and so Current (I)=0.

If you start getting into splitting currents, then this can be solved using Maxwells Circulating Currents.

Other tips: Back in my day, diodes created a 0.6 to 0.7 volt drop (when put the right way round).
• 06-02-2002, 06:11 AM
Ed Mack
Thanks.. I suppose I'll have to send some sort of internal ping around, and see if it's a complete circuit.
• 06-06-2002, 09:14 AM
hexagone
And don't forget Kirchoff's Law!!!
hex
• 06-06-2002, 12:09 PM
Ed Mack
Now your just taunting me. What is it?
• 06-06-2002, 12:18 PM
brutfood
Indeed it may be useful to you.

http://library.wolfram.co.uk/examples/kcl/
• 06-06-2002, 08:26 PM
magnetos
Kirchoff's Law!!!??

let me see if i remember right
Kirchoff's Law states that the sum of all the currents entering a node is equal to the sum of the currents exiting
the node

and the value of I in the node itself is 0
am i right???

• 06-07-2002, 06:32 AM
hexagone
You are indeed correct!
• 06-07-2002, 04:29 PM
Ed Mack
Show off. I already know that, not just it's name. Well, I bet you can't recite Robert Stanex's Special case Tennis rules.
• 06-07-2002, 08:56 PM
brutfood
Quote:

Originally posted by Ed Mack
Robert Stanex's Special case Tennis rules.
I tried finding that using Sherlock. It gave me a site in the Czeck republic- that I was refused access to browse.

Maths and theorem names can get terribly abstract and esoteric. I always need to visualise what is actually going on.

Electricity is about the flow of electrons. Voltage is about a potential difference in the number of electrons in one place and another. And where you have a difference in electron pressure - electrons will attempt to flow to equalise this.

In the early days of study into electricity, they has no way of knowing which way this electron flow was happening. They had a 50% chance of guessing right - and they guessed wrong. So current flows the opposite way to electrons.

If you were to sit at any point in the circuit, and count the electrons as they passed. Once you counted up to 1.6 x 10 to the power 19 electrons. This is called one 'Coulomb'. If one Coulomb flows per second - then you have one Ampere of current. (going the opposite way).

Kirchoff's law makes sense. If you sit at a node counting electrons - the number flowing in will equal the number flowing out. They're not going to sit around to take a break.

Of course, no post in this thread would be complete without someone introducing and naming a new theory or principle. :)

Earlier I gave a URL to an example of using Kirchoff's law to solve the currents in practical example. The calculation involved solving a matices equation.

A good way to do this, if you were coding it in Actionscript, would be to use:-

'Gaussian Elimination'