Electrical question about the direction of D/C current flow

[joshlee]

Hello everyone, I will use a general example of the light on a tractor. When you turn the light switch on, does the D/C current flow from the positive post in through the switch, through the light and into the frame, or does it come in through the frame first (negative post) then through the light to the switch?

Thanks everyone,
Josh

 

[oosik]

Current convention says DC flows from negative to positive.

 

[boggen]

a diode is like a check valve in hydrulaics, to water, to air. but for electricity. a LED "light emitting diode" requires correct direction of current to light up the LED bulb. or it will not light up at all.

 

[CobyRupert]

(It's all relative)
1. Assuming the battery is negative post is "grounded" to the frame (let's call this 0 volts), we "think" of the current flowing from the (+12 VDC) positive post to the (0 V) negative post.
2. If the positive post was "grounded" to the frame, we would also "think" of the current flowing from the (O Vdc) positive post to the (-12 VDC) negative post.


However, where we "think" of the current flowing from positive to negative charged posts, the current, i.e. the electrons themselves are negative charges (remember from high school chemistry class where protons are +1 charge, electrons are -1 Elementary charge - Wikipedia, the free encyclopedia) , so I believe they actually flow to the positive terminal (i.e. opposites attract). But ignore this, and say current flows from positive to negative.

Why do you ask, cause it's really arbitrary how we "think" about it? Are you wondering which way to insert a diode?

 

[CobyRupert]

I didn't read the article, but the pictures are great regarding: "conventional vs electron flow", including diodes.
Conventional versus electron flow : Basic Concepts Of Electricity - Electronics Textbook

The author says it better: "Many people choose to make conventional flow (positive to negative) their notation of choice when drawing the direction of charge motion in a circuit. If for no other reason, the symbols associated with semiconductor components like diodes make more sense this way. However, others choose to show the true direction of electron travel so as to avoid having to tell themselves, "just remember the electrons are actually moving the other way" whenever the true direction of electron motion becomes an issue.

 

[bcp]

Simple explanation:

Electron flow and conventional current flow - d.c. theory - (science -campus)

Bruce

 

[jaotguy]

for a simple "light" it doesn't matter ... but for some electronics , it is very important what gets connected to what ... ( try hooking up an alternator backwards or connecting 2 batteries up incorrectly) ...


Europeans follow the NEG ground now also, but "break or switch" the ground wire instead of the positive side.

 

[bcp]

Europeans follow the NEG ground now also, but "break or switch" the ground wire instead of the positive side.

Like this? Any reason one is better than the other?

 

[joshlee]

I'm not inserting a diode; I understand A/C current, but D/C just always puzzled me when I would think about which way the current comes into and goes out of whatever it is I'm wiring on a D/C circuit.

 

[DarkBlack]

How is possible to understand AC, but not DC? :jaded: