My textbook says that the flow of current is from the positive to negative and my notebook say that the flow of electrons is from negative to positive.
Why aren't they agreeing on one direction? Who is correct?
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$\begingroup$ Possible duplicates: physics.stackexchange.com/q/17109/2451 and links therein. $\endgroup$– Qmechanic ♦Apr 20, 2017 at 4:52
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3 Answers
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When electricity was discovered, scientists at that time were not aware of electrons. They thought that positive ions were responsible for current. Therefore, they decided that the direction of current would be from positive to negative. We still respect this convention even today.
After a century, J. J. Thomson discovered electrons. It was soon understood that electrons were responsible for current in most conductors. Changing the convention seemed to be a bad idea. Hence, we continued to use the same convention.
TL;DR: By convention, current is assumed to travel from positive to negative direction. The electrons travel from negative to positive. The direction of current is not the same as direction of flow of electrons; they are opposite.
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$\begingroup$ Could you elaborate on how/why the terminals of their batteries were chosen in such a way (+/-) and not the other way around? Also, who decided that the electron would have a negative charge? $\endgroup$ Mar 1, 2017 at 13:33
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$\begingroup$ The names for the two types of charges had already been well established before the electron was discovered. When J.J. Thomson performed the cathode ray tube experiment, it was discovered that electrons are negatively charged as they moved towards the positive plate. For a battery, the terminal at higher potential is chosen to be positive and the terminal at a lower potential is chosen to be negative. $\endgroup$– YashasMar 1, 2017 at 13:48
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$\begingroup$ And "higher/lower" potential would be defined as what? $\endgroup$ Mar 1, 2017 at 14:52
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$\begingroup$ 5V, 10V, -50V; 10V is the highest among the 3 and -50V is the least among the three. $\endgroup$– YashasMar 1, 2017 at 14:58
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$\begingroup$ Well yes, but in the end these are measured somehow and if I reverse the scale (different measurement device) I could have as well measured -5V, -10V, 50V. Basically what I wonder is whether the choice of +- is completely arbitrary or related to something fundamental. $\endgroup$ Mar 1, 2017 at 15:04
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Why aren't they agreeing on one direction?
Electric current is the flow of electric charge; electron current is the flow of electrons (which carry negative electric charge).
Put simply, a flow of positive charge in a given direction is electrically equivalent to a flow of negative charge in the opposite direction.
The convention is that the direction of electric current is the direction of positive charge flow.
And so, a flow of negative charge, e.g., a flow of electrons, is in the opposite direction of the electric current.
Had the charge convention been such that the electron charge is positive while the proton charge is negative, then the direction of electron flow and electric current would be the same.
It's a bit inconvenient that the electron is (by convention) negatively charged since most electric currents in electronics are due to electron flow (notable exceptions are the electric currents due to positive ions in, e.g., electrolytes).
But the convention is quite easy to get used to as long as you're careful to distinguish between electric current and electron current.
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Why we do not think this why that the flow of electrons are from +ve to negative not from negative to positive. I am giving reason for such type of thinking , the terminal is +ve because there is lack of electrons means we extract some of the electrons from that terminal and that election goes in the connected Cricut which is good conductor of electricity ( having metallic bond between its atom means reach of free electrons) , that electron pushes the electrons present in conductor that will give push to another electron and this crosses goes on.
