I'm just stepping all over myself on this one! I KNOW it's 1.0-1.35 ohms, not K ohms, but wrote it with a "K" anyway!! A ballast resistor/resistance wire the only application I'm familiar with that isn't in hundreds or K (thousands) ohms -- habit prevailed!! On November 8, 2005 Tom Jennings wrote: > Um, here's some poop on ignition coil resistance and resistance wire > in general: > > Modern coils need to charge up quickly to operate at high RPMs. To do > so they have fewer turns on the primary; at low speeds, once the coil > is charged up, the excess current turns to heat -- lots of it. The > series resistor does not slow down the quick charge-up, yet limits > the excess current at low speeds. > > Many cars jump around the resistor during cranking to give a little > boost to the spark. It does pass excessive current through the coil, > but not for long enough to do any harm. > > (The value of these resistors is around 1 (one) ohm, not K, which is > "1000". Most I've seen are 0.85 or 1.35 ohms.) > > With a points car, if you turn the ignition ON (engine not running) > and the points are closed, you'll see something 5V - 8V on the coil > "+" terminal. That's because about 10 milliseconds after you turned > it on, the coil was fully charged -- what you're seeing is the steady- > state voltage, which doesn't even matter. > > What you are NOT seeing is the current flow (not voltage, current) > through the coil, and you can't see the total energy stored in the > coil as a magnetic field, and that's all the matters. > > Current flow through inductors (coils) and capacitors/condensors is > dynamic, you can't see it with a voltmeter simply because it happens > too quickly. You can see it on an oscilloscope. > > I teach and demo this stuff as a part of my job. > > > > Coils charge up when the points (or electronic equivalent) are > closed, making current flow through the coil, building up a big > magnetic field. > > Ignition coils discharge, into the spark plug, when the points (..) > open. ============================================================= Posted by wixList Archiver -- http://www.amxfiles.com/wixlist