Edexcel Physics Unit 2 "Physics at work" June 2013

I referred to the equation R=(rho x l)/A and said that R is inversely proportional to A and directly proportional to l.As l increases and A decreases so R would be higher.Am i right?

What did people put for question 10, which is not involved in this, i ticked polarisation, because reflection, refraction, and superposition were all happening

yepp ... polarization does happen but it is not involved in the interference pattern

Hi guys. Thought it was a good paper, until it got to the last question I put resistance would be lower at a lower current because of less heating, so fewer ionic vibrations and less electron-ion collisions. Seems like I was in the minority. Thoughts?

I put resistance would be lower for the same reasons you did and in series

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Series, because if one bulb went out the other one did too.

I said this as well.

For last Mcq I put polarization. and for one with angle of incidence and angle or refraction I did 90- whatsoever the angle with horizontal. and angle of refraction was smaller value.

I got mgh/VIT for the efficiency, even though some said it was 0.5mv^2/VIT.

I also put superposition for the final MC but apparently it was polarisation. Silly me for not reading the q

I said this as well.

wtf

It is polarisation. Reflection was present

http://www.physicsclassroom.com/class/light/u12l1e.cfm#refln

So polarisation was present as there's polarisation by reflection.

i dont think it wanted you to put that, i thought about it but read the question over and over a few times then decided against it, you had to use equations such as V=IR

Yes I did, bloody annoying. That's the way the papers seem to be going. It's crap because you have to spend longer writing wordy answers and then you have less time to check over. But you also have to spend longer checking over! Sucks. Plus I love maths.

By the way, what did everyone put for a 3 mark question on defining plane polarised light? 3 marks??!! I think I said oscillates in one plane only, transverse and can be achieved using a polarising filter.
And two marks for defining a photon? I said it was a particle used to describe light, and that it was a discrete packet of energy or something like that.

so you think R increases
as for the photon question , the one worth 2 marks .. I said
A photon is a discrete quantum of electromagnetic radiation
is this good enough for 2 marks?
and for the polarization question I said:
The wave oscillates only in one plane perpendicular to its direction of propagation. Only transverse waves can be plane polarized ( and I drew a diagram of oscillations in one plane perpendicular to the direction of movement)
As for the corrosion question I got a value of 1.5 cm .. is that what you got?

Yes!

Someone put the Unit 1 paper on here very quickly this year, hope they do the same with this paper if it's possible!

I think for the last one the question asked us the effect of low current on the resistance of the bulb, so it wasn't asking for us to use any formulas, but use the fact the temperature would be less due to less current, so the ions in the lattice would have less energy and vibrate less, leading to less electron-ion collisions etc etc, so the resistance would reduce. That's what usually happens when a lamp is operating below it's normal rating, there is a low resistance which could give rise to a huge surge in current momentarily if a significant potential difference is applied

I said it would increase. I actually tried this on the calculations too, just to make sure it made sense, like, I lowered the current and the resistance did increase

Someone put the Unit 1 paper on here very quickly this year, hope they do the same with this paper if it's possible!

I think for the last one the question asked us the effect of low current on the resistance of the bulb, so it wasn't asking for us to use any formulas, but use the fact the temperature would be less due to less current, so the ions in the lattice would have less energy and vibrate less, leading to less electron-ion collisions etc etc, so the resistance would reduce. That's what usually happens when a lamp is operating below it's normal rating, there is a low resistance which could give rise to a huge surge in current momentarily if a significant potential difference is applied

Current causes a heating effect, so lower current means lower temperature of wire. Hence atomic vibrations decrease and since these atomic vibrations impede current, lower wire temperature causes a lower frequency of collisions between atoms and electrons. So resistance decreases with lower current.

Wrong or right? I think logically it makes sense.

So you think there is a good chance that I will get full marks in these parts?