View Single Post
 
Old 07-28-2012, 07:20 PM
TeslaSecrets TeslaSecrets is offline
Senior Member
 
Join Date: Jul 2012
Posts: 121
Some math for you.

In mathematics, dividing by zero is undefined. In electrical theory, we can divided by zero and get a valid result. I can demonstrate this with Ohm's law, which is relevant to what happens in a magnetic gap.

In a car ignition system is an induction coil. This coil is energized and then the circuit is opened or broken. We have voltage and current flowing in the coil, and then the circuit is opened. So our resistance effectively jumps to an infinite value. For any amount of current flow, when the resistance increases to infinity, the voltage will try to increase to infinity as well. This is according to Ohm's law and is the principle used to create the high voltage for the spark plugs in the engine. Voltage = Current x Resistance.

If say the ratio of the windings in the ignition coil was 100:1, for 12 Volts of power from the cars electrical system, we would get 1200 Volts of output from the secondary of the coil ( 12 X 100 ). In fact using the above application of Ohm's law, we get an inductive spike or inductive kickback in the primary circuit, when the break is opened. Thus the primary goes many times higher than 12V, increasing the resulting secondary voltage output. The output of these car ignition systems is typically higher than 5000 Volts.

You energy gurus should recognize the above concept is being used to recharge batteries running electric motors, to greatly increase efficiency and extend battery life.

We can apply the reverse of this formula as well. If we have an open circuit, at some voltage and connect it. The resistance goes from infinity to basically zero. So when we try to calculate current, we get Current = Voltage divided by Resistance, but resistance is zero. So mathematically this is undefined. However, nature obeys this reaction despite mathematics failure. The current does try to approach infinity, but is eventually limited by the true resistance and voltage.

This is what happens when you throw the breaker on a high voltage DC circuit. For a brief instant, current approaches infinity.

In a magnetic gap, whose electromagnet is powered by this same current, for a brief instant, the magnetic field approaches infinity, and thus the breaking force on the arc, approaches infinity.
__________________
 
Reply With Quote