Ok some monday morning discussion:
As this is the flathead forum lets use a 1939 Ford V8 and helmet distributor with dome coil and a dash mounted resistor. (contact points)
Both the coil and the resistor are approx .6-.7 ohms resisitance each for a total of 1.2 ohms ( cold) to 1.4 hot . Current flow will cause the resistance to increase somewhat.
The battery is 6 volts and 7.2 volts running at full charge down the road.
Using ohms law total resistance of 1.2 ohms divided into the 6 volt battery voltage would give us 5 amps of primary current.
Actually this would be the maximum current, as flow will cause the current to drop off ( 1.5 ohms hot would = 4.28 amps flow thru the circuit) .
Using these numbers i would say that the 6 volt system should never exceed
5 amps of primary current .
Change any number in this circuit and the numbers and current change......
