Re: Points...what do they do exactly

Posted by JMOR on November 21, 2008 at 10:00:15 from (76.187.218.177):

In Reply to: Points...what do they do exactly posted by Hugh MacKay on November 15, 2008 at 10:11:24:

LenNH said: (quoted from post at 17:51:00 11/20/08) Some useless but maybe interesting comments: Michael Faraday discovered that current in one coil would induce current in another coil nearby. I don"t have the dates exactly, but I think it was around 1830. A few years earlier, another researcher, a Dane named Oersted, accidentally discovered that a current in a wire creates a field around the wire (he noticed that bringing a compass near to the wire caused the needle to move)(Uri Geller tried to show that he could do the same thing using his magical powers; turns out he used tiny magnets). Faraday took up where Oersted had left off. The farad is named for Faraday. Other useless information: the original condensers were big glass jars (Leyden jars)lined inside and out with foil. Static-electricity generators fed current to each side of the glass. When the current was released, there could be quite a jolt. Seems it was a parlor trick in the late 1700s to shock your guests with current in a Leyden jar. Other terms named for individuals: Ohm and ampere. Poor Mr. Oersted apparently didn"t get anything named for him. Some of the writers answering say that the ignition system will work without a condenser. I have seen engines--way back when--that wouldn"t run when the condenser failed. Has anyone seen an engine run without a condenser? Perhaps with a very wide gap, to make it hard for the current to jump the gap? The condenser certainly has the function of keeping the points from burning (because the electrical current "wants" to keep going across the gap and will make a considerable spark without a condenser to absorb the current briefly), but it is also true that if the current continues across the points, there will not be much of a breakdown in the magnetic field across the secondary winding of the coil, hence a very weak or maybe even no spark. Hope I"m not repeating what others have said.

Well, Len, don't feel too sorry for poor old Hans Christian Oersted, as he did make it into history........

Oersted, a unit of magnetic field intensity, symbol=H, the units being amperes/meter. He and many others just didn't make it into the vocabulary of the masses, along with names such as Joule (energy) and Weber (vector magnetic potential).

With NO condenser at all, soooo much of the energy is lost in the arc across the opening points, that little remains to be delivered at the secondary for the plug. Yes, there is a little, but unless you were to gap the plugs very, very small, the running of an engine like this is truly a hit & miss situation, i.e., rare & poor. I have never made it happen, even though I have observed the very small spark.

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