Connecting up the coil

Following the article in the October TTT 2 two responses were received as follows:

Graham Knight posted the following comment:

“Thanks very much for an interesting article but I’m having trouble understanding the explanation. I don’t see that reversing the polarity changes the path the electrons take nor the resistance they encounter. Doesn’t it just make them flow in the reverse direction?

I came across this: which confirms that polarity is important but for a different reason. That is that the central electrode of the sparking plug needs to be negative since electrons prefer to jump from hot to cold.”

Graeme Hogg posted the following comment:

“I too have been confused as to correct coil polarity and when researching the subject came up with two articles that appear to disagree with Steve and John’s conclusions as to the correct way around to connect the coil. Both also suggest that spark plug polarity is the more important factor.

Moss Motors at Coil Polarity and MGA Guru at make for interesting reading. Perhaps Steve might check his spark plug polarity as described in the two articles and observe whether his current coil connection gives the “correct” plug polarity as defined in the articles.”

Peter Cole and Eric Worpe also contacted me and they have kindly produced the following article, starting from first principles.