# Britsh physics olympiad 2022 (y13)

https://www.bpho.org.uk/Papers/PC/

Question 4)b)iv) on the 2022 paper:
Why is the potential difference zero? The person removed the bulb so wouldn't current flow through the rest of the bulbs and it would be a standard series voltage question?

I've looked at the mark scheme it doesn't provide much help.

No current flowing means no voltage dropped by the bulbs. V=IR

They're measuring between Z and X and there's no voltage dropped by the bulbs
Original post by Joinedup
No current flowing means no voltage dropped by the bulbs. V=IR

They're measuring between Z and X and there's no voltage dropped by the bulbs

How is the current zero, isn't the faulty bulb removed?
Original post by 17beqire
How is the current zero, isn't the faulty bulb removed?

Its a set of series bulbs, how much current flows through a removed bulb?
Original post by Joinedup
Its a set of series bulbs, how much current flows through a removed bulb?

It's asking how much current flows through the rest of the circuit when the bulb is removed, how would that be zero?
Original post by 17beqire
It's asking how much current flows through the rest of the circuit when the bulb is removed, how would that be zero?

You understand what series means?

Current comes out of one component and goes into the next component all the way along.

If any component is removed that cant happen anymore and all the components get no current.
Original post by Joinedup
You understand what series means?

Current comes out of one component and goes into the next component all the way along.

If any component is removed that cant happen anymore and all the components get no current.

Oh I thought bulb 6 gets removed and the remaining bulbs get joined up again.
Original post by 17beqire
Oh I thought bulb 6 gets removed and the remaining bulbs get joined up again.

Yeah maybe the question writer is assuming people have seen these old lights... They had 20 tiny lampholders soldered into a loop of wire in series. the bulbs were replaceable so you could take any bulb out of its holder - sure that's what theyre talking about here.