|MadSci Network: Physics|
Hello Andrew Since I don't know how much you know, I may cover something you are familiar with. The ignition is a transformer. This means it is two coils that are magnetically coupled to each other. One of the coils is called the primary and the other is called the secondary. The secondary might have 100 times as many winding as the primary. When you attach a power source to the primary, current starts to flow in the primary coil. This causes a magnetic field to be created. The field builds quickly to full strength. The field does not build instantly because the increasing magnetic field (in the primary) actually resists any further increase. (This is called self-inductance). Finally the primary reaches steady state. The field is maximum and the current flowing in the primary is limited by the resistance of the primary coil and the voltage of the power source. The magnetic field that is created by the primary has moved across the secondary coil as the field expanded. The expanding magnetic field causes the secondary coil to develop a voltage to force current to flow. Since the secondary coil has many more windings, it develops a larger voltage. If the ratio (as I originally made up) is 100, the secondary will develop 100 times the voltage to drive the current. So we might see 1200 volts from a 12 volt primary source. You can test the validity of the paragraph above by winding your own transformer. You can also pass a large magnet by a coil of wire and observe that a voltage is produced in the coil. This is because the magnetic field of the permanent magnet is moving across the coil. If there is no movement, there is no voltage created. Now for the big bang. When you disconnect the power source from your coil, the current flow through the primary stops. The magnetic field collapses very rapidly. The lines of magnetic force move past the windings in the secondary more rapidly in the collapse than when the magnetic field was built. The secondary voltage can be many more times the 1200 volts it may have reached when the coil was energized. 12,000 volts might be achieved. IF you still have questions, write back to MadSci. Gus Calabrese
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