Electron flow in a car circuit

Thread Starter

Clive45

Joined Nov 5, 2017
1
I work in the automotive sector, with experience of refurbishing alternators and starter motors. It always puzzled me when told the electron flow from neg to pos - why? Because logically AC current is produced by the alternator, sent to the rectifier and then bumped up to very high voltages at the HT coils and then discharged through the spark plug. Surely the electron flow implies current flows the other way? The same principle would apply for the starter circuit too. Even allowing for Hole theory (?) it's all a bit bizarre really. As humans have we somehow missed a fundamental law in our perception of how current really flows I wonder? Do we truly understand electron flow and is hole theory proven scientifically?

Clive.
 

dl324

Joined Mar 30, 2015
9,576
As humans have we somehow missed a fundamental law in our perception of how current really flows I wonder? Do we truly understand electron flow and is hole theory proven scientifically?
Ben Franklin had a 50:50 chance of guessing right and he guessed wrong. We know he was wrong because it was proven scientifically.

We rarely talk about electron flow. It's used when it makes more sense than using conventional current flow, e.g. when talking about CRTs.

Books have been written using both conventions. If you're used to one, the other might seem confusing. Everything works out as long as you're consistent. However, if you want to be mainstream, use conventional current flow.
 

crutschow

Joined Mar 14, 2008
24,074
Electrons are the electricity charge carrier in normal conductors.
Holes (the absence of an electron) as carriers only occur in semiconductor theory and, yes, it is fully proven.

There are two conventions for viewing current in a circuit.
  1. Electrons flow from the negative the to positive side of a circuit.
  2. Conventional current flow which assumes an imaginary positive carrier, flowing from positive to negative.
You can use either electron flow or current flow in the analysis of circuit but use only one or the other, or you will tend to confuse yourself.
Mathematically both conventions lead to the same results in calculating a circuit's operation.

Yes, both current flow and electron flow are fully understood.
Your apparent confusion appears to be from mixing the two concepts.

In a vehicle with a negative ground to the frame (all modern vehicles) the conventional positive current flow is from the alternator or battery, through the various circuits, to ground and back to their negative terminals.
The electron flow from the same vehicle would be out of the negative battery terminal and alternator ground, through the ground to the various circuits and back to the alternator output/battery positive terminals.
 

MaxHeadRoom

Joined Jul 18, 2013
19,685
then bumped up to very high voltages at the HT coils and then discharged through the spark plug. Surely the electron flow implies current flows the other way?
A automotive spark plug generally prefers to see a voltage potential that is negative on the center electrode of the plug, this has nothing to do with polarity of the vehicle electrical system, but it is influenced by the common connection inside the ignition coil.
Max.
 
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