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.

Can someone please help me on this?

Reply 1

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

Reply 2

17beqire

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?

Reply 3

Joinedup

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?

Reply 4

17beqire

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?

Reply 5

Joinedup

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.

Reply 6

17beqire

Original post by Joinedup

Oh I thought bulb 6 gets removed and the remaining bulbs get joined up again.

Reply 7

Joinedup

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.