physics

[pillar]

common knowledge is that current is the convectinal flow of current and current flows from -ve terminal to +ve terminal.How threforee is it that current flows from +ve to -ve?

[mibn2cweus]

No surprise, you�ve got it backwards, kinda . . .

Conventional current flow was determined before they actually knew which way current flows. It was though it flowed the other direction from the �greater (positive)� to the �lesser (negative)� potential.

Current is mostly due to the direction of flow of electrons which actually move from the previously thought �negative� toward the �positive� potentials. The reverse 'negative' and 'positive' designations have been retained in spite of this error because these labels were already in wide use when the error was discovered.

To add to the confusion, less prevalent ionic current flow IS from �positive� to �negative�. The conventional current flow is still the norm widely used so that the maths add up correctly.

I'll check back later when I've finished verifying my 'facts'.

[matt1e]

you are slightly wrong here conventional does not flow from -ve to + ve but the other way around ie +ve to -ve this is because all the theories and conventions were already in place before it was discovered that current was actually due to electron flow which flows from negative to positive so basically
we have
conventional flow = pos to neg
actual flow neg to pos
thing get a little complicated when we get to current flow in materials other than metals as the electric current is due to the flow of charged particles in both directions at the same time so for simplicity the idea of conventional flow is still used

[matt1e]

just to clarify something here when i say that you are slightly wrong here conventional does not flow from -ve to + ve but the other way around ie +ve to -ve
I mean to say that the IDEA of current flowing from pos to neg is called conventional current flow and that is still used today in drawing etc even though we now know that the opposite is true ie neg to pos
hope that helps

[chakka35]

Yes, they got it wrong at the beginnng and have chickened out of correcting it. The right time to have done that was when semiconductors (transistors and so on) came into view. Explaining how a transistor works (using the flow of electrons) and then having to tell the learner that they should ignore all that and treat the arrow on the symbol as being a positive flow is an absolute pest. In any case there is no positive flow because the positive-charged ions stay in place while the electrons move. Sheer cowardice.