Posted by arthur p bloom on Saturday, June 19, 2004 at 8:48PM :
In Reply to: Why doesn't gas gauge sender cause an explosion posted by Jim Chance on Saturday, June 19, 2004 at 7:18PM :
The reasons are as follows:
The gauge is a resistive component. Resistors "resist" the flow of current (measured in amps). The higher the resistive value, the lower the current.
The fuel sender is also a resistor. There is a very small amount of current flowing through the circuit; so small, in fact, that it is virtually impossible to cause a spark.
The sliding arm on the sender is theoretically in contact with the windings of the sender's armature at all times, and moves onto a new winding before moving off the previous one. (Called "make-before-break" in the electrical biz.) Therefore, once again, the design limits the potential of a spark.
In addition, the fuel-to-air mixture within the tank is so rich that there isn't enough oxygen to support combustion. (Please don't try this at home, but one can demonstrate this by throwing a lit cigarette butt into a pail of gasoline, with less than dramatic results.)
Did you know that many electric fuel pumps are directly immersed in the gasoline, and the gasoline supresses the sparks in the motor? Weird, but true.
APB
Follow Ups: