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I'm rather new to this and am slightly confused about which direction the electrons actually flow. Using an LED with the knowledge that conventional current flows out of the cathode, and hence the opposite is true for electron flow, it seems electrons actually flow out of the ground pin. Is this correct?

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    \$\begingroup\$ You are completely confused. Conventional current is positive to negative, but actual (electron carrier) current is negative to positive. This has next to nothing to do with the rapsberry pi. \$\endgroup\$ – Chris Stratton Feb 1 '16 at 0:03
  • \$\begingroup\$ Possible duplicate of Which way to draw diode in a circuit diagram \$\endgroup\$ – The Photon Feb 8 '16 at 1:43
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Do electrons flow from the ground pin? Yes.

Does it matter? No.

Do you have to connect the LED the way the diagram shows, or backwards? The way the diagram shows.

Because electrons flow from the ground instead of the +ve supply, do you have to connect the LED the opposite way to the way everybody else connects it? No, the same way as everybody else does.

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Positive to negative current flow was established before the discovery of the electron by J.J.Thomson in 1897. We still use the convention for most practical electrical and electronics but we keep in the back of our heads that the charge carriers are actually electrons moving the other way.

schematic

simulate this circuit – Schematic created using CircuitLab

Figure 1. Diode, Zener, LED, photo-diode, SCR (thyristor), NPN and PNP transistors all point in the direction of conventional current flow.

All of our diode and transistor symbols show use arrows to show the conventional current flow.

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    \$\begingroup\$ Since a Zener Diode is normally used reverse-biased, it is installed pointing against the conventional currrent flow \$\endgroup\$ – Peter Bennett Jan 31 '16 at 23:02
  • \$\begingroup\$ Of course it was established before the discovery of the proton also. What's your point exactly? \$\endgroup\$ – Phil Frost Sep 8 '17 at 2:07
  • \$\begingroup\$ My point is that many beginners are confused by why conventional current flows positive to negative while, in most cases, the mobile charges are electrons flowing the opposite direction. When one realises that the current convention was established before the knowledge of sub-atomic particles was then the problem is solved. Protons are not mobile so I didn't mention them. Does that make sense? \$\endgroup\$ – Transistor Sep 8 '17 at 6:39

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