If you hook a lightbulb up to a battery, from the negitive terminal to the positive terminal you will have 12v.
If you measure from the negitive terminal to the input to the bulb you will have 12v
If you measure from the negitive terminal to the output of the bulb you will have 0V.
If you measure from the negitive terminal to the negitive terminal you would have 0v
If you measure from the negitive terminal to the output of the bulb with the output of the bulb disconnected from the negitive terminal you will have 12v
