0
\$\begingroup\$

I'm following an introduction in circuit electronics, and there seems to be a contradiction in its explanation of the direction electricity flows. First it says that electricity is the movement of valence (outer shell) electrons from atom to atom, and that the negative pole of a power source (being of like charge) will push electrons from the negative pole and electrons will flow from the negative pole to the positive pole, which attracts flowing electrons.

Then I've come across this description:

the positive side will have a higher voltage than the negative side, which is exactly what we want. In fact, when we measure voltage, we usually say that the negative side is 0 volts, and the positive side is however many volts the supply can provide.

What have we learned so far?
*Electricity will flow from a higher voltage to a lower voltage.
*DC voltage sources always have two sides, called positive and negative, with the positive side a higher voltage than the negative side.

The bolded part especially seems to contradict what was said earlier about the flow being from negative to positive.

Here is the link to the site

Could someone explain how the electricity in one explanation flows from negative to positive, and in the other explanation from positive to negative?

\$\endgroup\$

1 Answer 1

Reset to default
0
\$\begingroup\$

Electrons flow from negative to positive. What we normally consider to be electric current flows from positive to negative. This is a historical oddity that developed because Benjamin Franklin knew something about electricity but nothing about electrons.

\$\endgroup\$
3
  • \$\begingroup\$ @DrMoishePippik Actually, the atoms do not move or flow, but there is an unconnected bond, or vacancy or hole, in the crystal lattice. If an electron moves from one bond to another then an equivalent point of view is that the hole has moved in the opposite direction. In reality, the electrons are the only physical matter that moves during current flow. \$\endgroup\$
    – Elliot Alderson
    Jul 13, 2018 at 10:45
  • \$\begingroup\$ Footnote: in semiconductors, holes, i.e. places where electrons are missing, do flow from positive to negative. Also, the diode arrow symbol shows the "traditional" flow of positive to negative, Franklin got so much right, and even started a hat fashion, so I don't begrudge him one error. \$\endgroup\$
    – DrMoishe Pippik
    Jul 13, 2018 at 16:25
  • \$\begingroup\$ Thanks... I had definitely mis-phrased that. BTW, neither individual electrons nor holes move fast; the electron velocity in copper at moderate currents is on the order of mm/second, about 10 orders of magnitude less than that of the EMF. \$\endgroup\$
    – DrMoishe Pippik
    Jul 13, 2018 at 16:31

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.