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I'm just starting out learning about Electronics but something has puzzled me . I have read that current flows through a circuit from negative part of a battery to positive .

but what puzzles me is I made a simple series circuit of a Diode - Resistor - LED ........... Positive terminal is connected to the Diode so how does the LED light up if electricity flows from negative to the positive terminal ? If electricity flows from negative to positive the Diode would stop the flow and the LED would not light up?

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marked as duplicate by The Photon, markrages, Sparky256, Daniel Grillo, Voltage Spike Aug 8 '16 at 18:48

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  • \$\begingroup\$ mi.mun.ca/users/cchaulk/eltk1100/ivse/ivse.htm Conventional current flow vrs electron flow \$\endgroup\$ – Tyler Aug 7 '16 at 23:18
  • \$\begingroup\$ Another related question: What exactly does a diode do? \$\endgroup\$ – The Photon Aug 7 '16 at 23:22
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    \$\begingroup\$ paul, one of the things you're just going to have to get over is the fact that, although electrons moving are what constitute current, the convention runs the opposite direction. It all goes back to a historic jelly-side-down choice about positive and negative. Stop worrying about electrons. Current flows from positive to negative. \$\endgroup\$ – WhatRoughBeast Aug 7 '16 at 23:25
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    \$\begingroup\$ Another thing you're going to want to get used to is using the usual conventions of English writing, such as capitalizing the first letter of a sentence, and placing the punctuation in the usual places. If you don't do this it will be hard for people used to reading English as it's normally written to take you seriously. \$\endgroup\$ – The Photon Aug 7 '16 at 23:26
  • \$\begingroup\$ Don't forget an LED is a diode. \$\endgroup\$ – pjc50 Aug 7 '16 at 23:28
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Conventional current flows through the circuit from the positive terminal to the negative. It's called 'conventional' because that's the convention we have all decided to use. It was standard before it was known that electrons have a negative charge and flow in the opposite direction. It doesn't matter which we use from a circuit analysis point of view, provided we all agree to use the same one- that one is that current flows from positive to negative.

The diode's schematic symbol has the 'arrow' in the direction of current flow when forward biased.

PS The link given by an above comment from @Tyler is amusing, and also makes reference to this xkcd comic.

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  • \$\begingroup\$ Tip: conventional current = hole current -- this simplifies things considerably, especially when you get to semiconductors. \$\endgroup\$ – ThreePhaseEel Aug 8 '16 at 0:35
  • \$\begingroup\$ Conventional current is a mathematical convention; it's not hole flow. Calculations are arguably easier with conventional current vs. electron flow math, although both yield identical results. \$\endgroup\$ – Jim Fischer Aug 8 '16 at 1:47
  • \$\begingroup\$ @ThreePhaseEel, your comment is plainly wrong. Conventional, i.e., electric current is simply the flow of electric charge where the direction is, by convention, the direction of the flow of positive charge. In a plasma, for example, there can be a flow of both positive ions and negative ions in opposite directions; both ion flows contribute to just one electric current in the direction of the positive ion flow. \$\endgroup\$ – Alfred Centauri Aug 8 '16 at 2:23
  • \$\begingroup\$ @AlfredCentauri -- and what carries that positive charge in the materials we care about on a day-to-day basis as EEs? Holes! \$\endgroup\$ – ThreePhaseEel Aug 8 '16 at 3:51
  • \$\begingroup\$ Conventional current flow is not hole flow; it is simply a mathematical convention--a set of rules for assigning voltage polarities across components--that facilitates systematic analysis of electronic circuits. \$\endgroup\$ – Jim Fischer Aug 8 '16 at 6:15

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