# electricity physics help neededWatch

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#1
Q) X and Y are two lamps. X is rated at 12 V 36 W and Y at 4.5 V 2.0 W. Image for question below
https://imgur.com/a/y9tiKAX

Just looking for confirmation or answers 2 questions:

to find pd of r1 is that you can consider X to be a series if the current walks the pathway there, so as voltage is split in series, u just - that up, to get pd of r1? If so so the parallel component doesn't affect that why?

So if the current in R1 is 3.44 A
Does this use kirchoffs law meaning sum of current before junction = currents of junction?

Calculate the pd across R2. why?

MARK SCHEME
(b) (i) pd = 24 − 12 = 12 V 1 (ii) current = 3.0 + 0.44 = 3.44 A 1 (iii) R1 = 12/3.44 = 3.5 Ω 1 (iv) pd = 12 − 4.5 − 7.5 V 1

(v) R2 = 7.5/0.44 = 17 Ω
0
#2
as well as this,

The filament of the lamp in X breaks and the lamp no longer conducts. It is observed that
the voltmeter reading decreases and lamp Y glows more brightly.
(i) Explain without calculation why the voltmeter reading decreases.
________________________________ ______

ms:
1(circuit) resistance increases
2current is lower (reducing voltmeter reading) - why does the current reduce, if x breaks theres no more 0.44 a running through it so why does the whole circuit revert back to 3A? wouldn't there be 3.44A initially?
3 or correct potential divider argument - what would this be?
0
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