the one is not light
When two light bulbs are in place, there will be a circuit created where electricity can flow through both bulbs. If the circuit is intact and the bulbs are functioning, they will both light up. If one of the bulbs is faulty or the circuit is broken, then both bulbs may not light up.
Plant bulbs or electric light bulbs? More information is needed.
As a series circuit, as asked, all bulbs will go off because of that just one bulb.
There are a few possible different results. One thing that happens in EVERY possible situation is that the bulb you unscrew is dark after you unscrew it. -- If the two bulbs are configured in either a series or a parallel arrangement and the power is off, then both bulbs are dark before you unscrew one, and nothing changes after. -- If the power is on and the two bulbs are configured in parallel, then the one you don't unscrew continues to glow after the other one is gone. -- If the power is on and the two bulbs are configured in series, then BOTH bulbs go out when you unscrew only one of them.
current in series always stays the same
You have to decide which place to go.
The other bulb remain to glow with same intensity.
The filament breaks.
nothing
Two bulbs in parallel are brighter than the same two bulbs in series, given the same potential voltage, because there is twice the available voltage to each bulb.
Of course. The circuit in my house has two door buzzers and almost 30 bulbs.
Normally this happens when one of the bulbs is burnt out. Make sure all bulbs are working.