Assume that the circuit shown in figure "A" of the illustration represents a two-wire single phase AC ground detecting system. If a ground occurs on line "B" as illustrated, which of the lamps will burn the brightest, before the test pushbutton switch is depressed? See illustration EL-0008.
• Two-wire ground detection circuit with two lamps in series across the lines • Effect of a single line-to-ground fault on the voltage between the two lines themselves • Role of the test pushbutton to ground vs the normal (open) condition
• Before the test switch is pressed, is there any complete current path that involves the ship’s hull/ground, or is the lamp circuit only connected between line A and line B? • If the two lamps are identical and connected in series across the same two line conductors, what happens to the voltage division between them when one line is additionally tied to ground somewhere else in the system? • Would grounding line B change the total voltage between A and B, or just give a reference point to earth? How does that affect lamp brightness?
• Confirm that, with the test switch open, the mid‑point of the two lamps is NOT connected to ground anywhere. • Verify that both lamps are still in series across the same A–B line voltage after the ground fault on line B occurs. • Remember that two identical lamps in series share the applied voltage equally unless something changes their series connection.
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