I d love it if somebody could add a bit on what the heck use it is My experience so far involves a physicist who always worked with A I was running physical experiments on the device he had derived a theory for He insisted the device would have no magnetic field I whipped out the gaussmeter and measured the magnetic field He would not accept the readings as he considered the B field an illusion Yet he was unable to direct me to an instrument that could measure vector potential and could not convert A to B due to the pesky gauge factor problem