This has been an interesting couple of days. My interest in the prop has lead me to have a brief discussion with Tom at Indigo. Nice guy, willing to share knowledge and experience. I've learned a lot.
Electronics is my weakest area of knowledge, but obviously, many of you have keen interest in the topic, so here's a question that came from my discussion with Tom.
Why is it a common belief on the Forum that just because a coil reads 4.0 Ohms across the brass studs, 3 Amps of current will flow through that coil when 12 VDC is applied across the stud?
The real answer is that Ohm Law, V=IR, only applies to a pure resistor. A
coil does indeed have resistance but it also has inductance, reluctance, and
impedance which makes Ohms Law not applicable. A very simple means of
proving this is to install a ballast resistor in an ignition system and then
measure the voltage drop across the resistor. You can then use Ohms Law to
determine the amperage. If you perform such a test, you will find that the
current through a coil with about 4 Ohms resistance and a 1 Ohm ballast
resistor with 13.3 VDC applied is only about 1.31 amps. Without the
resistor, the current is about 1.55 amps.
Ok, do what you will!
Chris
Skywalker
Electronics is my weakest area of knowledge, but obviously, many of you have keen interest in the topic, so here's a question that came from my discussion with Tom.
Why is it a common belief on the Forum that just because a coil reads 4.0 Ohms across the brass studs, 3 Amps of current will flow through that coil when 12 VDC is applied across the stud?
The real answer is that Ohm Law, V=IR, only applies to a pure resistor. A
coil does indeed have resistance but it also has inductance, reluctance, and
impedance which makes Ohms Law not applicable. A very simple means of
proving this is to install a ballast resistor in an ignition system and then
measure the voltage drop across the resistor. You can then use Ohms Law to
determine the amperage. If you perform such a test, you will find that the
current through a coil with about 4 Ohms resistance and a 1 Ohm ballast
resistor with 13.3 VDC applied is only about 1.31 amps. Without the
resistor, the current is about 1.55 amps.
Ok, do what you will!
Chris
Skywalker
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