Why did Titanic's lights stay on while she was under water sinking. And Why did they suddenly go off just before she split in two?

Answer 1

There are several theories as to why her lights stayed on as long as they did.

First, lets set out the known facts:

1). Titanic's electrical generators were run off steam, the same as the engines. As long as there was enough pressure from the boilers (regardless of whether they were lit), the electric generators would continue running, even if the engines were stopped.

2). Titanic's lights ran on 100v direct current (DC, unlike AC - alternating current - used today). Her lights would have remained on even underwater (to a certain extent). This is similar to you turning on a flashlight and dropping it into a bathtub or a pool. The light will stay on, albeit dimmed.

As far as her sudden loss of power, there could be several reasons.

One is that steam pressure just ran out. This is unlikely though, since the boilers were venting their pent-up steam through the funnel's steam pressure exhaust pipes all night.

Another possibility is that electrical lines broke, though I find this unlikely, as the dynamos were located in the stern, behind the main reciprocating engines. If this had happened, the stern's lights would have remained on

A third, more likely, scenario, is that the steam pipe from the boilers broke or was breached at some point, depriving the electrical generators of their needed steam.

Hope this helps!