Edexcel Physics Unit 2 "Physics at work" June 2013

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I put D but unfortunately I've realized it must be C :frown:

The question doesn't tell us which way the wave is moving, it is a displacement TIME graph. We can't use the 'tracing' method, so yeah we were tricked :redface:

The only possible option is C

Can you elaborate further?
i don't really see what you mean. If it was a displacement time graph you cannot work out the wavelength which would explain why my method is incorrect, leaving C as the only possible answer but there has to be a better explanation ?

Reply 881

RoyalBlue7

Original post by x0x

Well that was not describing the wave.
The graph was describing the (simple harmonic) oscillations of one point in the wave to another, so hence displacement vs time

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Reply 882

Alexsk

Original post by x0x

The one about S and O (one is a source the other is an observer)
i think the answer is C .. both move towards each other so frequency increases?

I put the option with S and O in opposite directions which said that frequency decreases! Wasn't there such an option?

Reply 883

x0x

Original post by Alexsk

I put the option with S and O in opposite directions which said that frequency decreases! Wasn't there such an option?

my bad! there was only one option with both going towards each other :P it doesn't matter hehe

Reply 884

GCSE-help

My MAIN concern is the last question. Does anyone have any clue what the hell the answer was? Can't believe it's been this long after the exam and there's so much disagreement over the answer. No textbook or internet source seems to be helping :mad:

Reply 885

Alexsk

1)Because it was a lamp I think it behaves like a filament lamp. As current decreases, heat decreases.
2) Therefore, the energy provided to ions decreases. Vibrations of ions decreases.
3)Less collisions with electrons.
4)Less resistance

Reply 886

GCSE-help

Original post by Alexsk

Now are you SURE about this? Have you had it confirmed by teachers etc etc. Because this is what I put and EVERYONE seems to disagree back in school. If it's right, I'm gonna be so happy.

Reply 887

Nathan@

Original post by StephenNaulls

I think your first answer is incorrect. The frequency was 216.8 MHz(around) so it had to be converted to 10^6 Hz and the powers cancelled to give just over 1m wavelength.

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Right on, i remeber that question now, i think the 1322.5 came from the resistance of the bulb later on in the exam

Reply 888

RoyalBlue7

Original post by Alexsk

What about voltage? Shouldn't the sum be equal to 230!!!!!!!!!

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Reply 889

GCSE-help

Original post by StUdEnTIGCSE

What about voltage? Shouldn't the sum be equal to 230!!!!!!!!!

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No because it was being operated at below it's normal rating! I think people are missing a massive key point. The question asked for the effect of low current ON the resistance. So it's not asking us to consider WHY the current was low, just accept that it was! And then we had to find the effect of the low current on the resistance!

Reply 890

hamzeh h

Original post by GCSE-help

Now are you SURE about this? Have you had it confirmed by teachers etc etc. Because this is what I put and EVERYONE seems to disagree back in school. If it's right, I'm gonna be so happy.

i wrote this and most of my classmates disagree

Reply 891

Alexsk

99% sure. The lamp is definitely not an ohmic resistor. Therefore R is not inversely proportional to I. Moreover, it cannot be a diode- semiconductor. So what is left? The filament lamp!!!

Reply 892

Phteven

Original post by Nathan@

Right on, i remeber that question now, i think the 1322.5 came from the resistance of the bulb later on in the exam

Yeah, I think that's what i got too. I remember getting a little worried because it was such a high resistance and quite a weird number. I'm used to them giving us a "normal" number like the 12.5 one we got just after!

Reply 893

Phteven

I feel like they could've worded this last question so much better. I know the theory behind resistance in a filament lamp. If that was what they wanted they should have made it clearer!!! :angry:

Reply 894

hamzeh h

Original post by Alexsk

99% sure. The lamp is definitely not an ohmic resistor. Therefore R is not inversely proportional to I. Moreover, it cannot be a diode- semiconductor. So what is left? The filament lamp!!!

are u alex from xtremepapers? :P

Reply 895

hamzeh h

Original post by StephenNaulls

I feel like they could've worded this last question so much better. I know the theory behind resistance in a filament lamp. If that was what they wanted they should have made it clearer!!! :angry:

ya it was kinda of tricky

Reply 896

hamzeh h

so the 3rd MCQ is it D or C ?

Reply 897

Nathan@

Original post by StephenNaulls

I feel like they could've worded this last question so much better. I know the theory behind resistance in a filament lamp. If that was what they wanted they should have made it clearer!!! :angry: