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# Edexcel AS Physics Unit 2 June 2016 watch

1. (Original post by Timlong365)
If this were a 5/6 exam question, I'd answer it like this:
Photons are discrete packets of electromagnetic energy. When radiation is incident on a metal surface, if the energy of the photon (given by E = hf) is greater than or equal to the work function of the metal, the electron absorbs its energy and gets emitted as a photoelectron. One electron absorbs the energy of one photon. Some of the energy absorbed is used to release the electron and the rest appears as kinetic energy (so E = workfunction + KEmax). It thus follows that as the enegy of the incident photons increases, the value of KEmax increases as well (so it varies with E or frequency of radiation). The value of kinetic energy is only a maximum as some energy is transfered to the metal during collisions with lattice ions while the electrons emerge from the surface.

Please correct me if anything you see is wrong/needs improving.
Thank you
2. Questionn:
According to the equation V=IR there were some questions that asked what happens when the potential difference increases. So we say that when potential difference increases the resistance increases as they are directly proportional. And when resistance increases the current decreases.

But isn't V also directly proportional to current? So why don't we say that as the potential difference increases the current increases. And as the current increases the resistance decreases?

Does this depend on the situation?
3. Please can anyone tell that why a voltmeter has high resistance and why an ammeter has very less resistance ??
4. (Original post by Becka99)
Questionn:
According to the equation V=IR there were some questions that asked what happens when the potential difference increases. So we say that when potential difference increases the resistance increases as they are directly proportional. And when resistance increases the current decreases.

But isn't V also directly proportional to current? So why don't we say that as the potential difference increases the current increases. And as the current increases the resistance decreases?

Does this depend on the situation?
Aah! I know that how much brain torturing this electricity chapter is.
Lemme tell u somethin' :::
Voltage is dir. proportional to resistance WHEN the current in the circuit is constant.(series combination)
Current will decrease with increasing resistance WHEN the voltage is constant.(parallel combination)
Then for the last point V is dir. proportional to current ONLY WHEN the CONDUCTOR is an ohmic conductor and OBEYS Ohm's law, in which resistance is constant when temperature remains constant.
I think this should explain you.
5. (Original post by Ahmed3651998)
Aah! I know that how much brain torturing this electricity chapter is.
Lemme tell u somethin' :::
Voltage is dir. proportional to resistance WHEN the current in the circuit is constant.(series combination)
Current will decrease with increasing resistance WHEN the voltage is constant.(parallel combination)
Then for the last point V is dir. proportional to current ONLY WHEN the CONDUCTOR is an ohmic conductor and OBEYS Ohm's law, in which resistance is constant when temperature remains constant.
I think this should explain you.
You are a lifesaver!!!!! Never had it laid out more clearly 👍🏻
6. Can someone plz explain me what is the reason behind the frequency of the lamp being maximum at 1320Hz? Question 18 (C)(iii).

Question paper

https://qualifications.pearson.com/c...-June-2014.pdf

Mark scheme

https://qualifications.pearson.com/c...-June-2014.pdf
7. (Original post by Ahmed3651998)
Please can anyone tell that why does a voltmeter has high resistance and why does an ammeter have very less resistance??
voltmeters have "infinite" or high resistance, so that the current flowing will not be drawn by the voltmeter, but will pass through the component that is being measured (which is the main reason y v connect it in parallel)

An ammeter will have very low or zero resistance, so that it does not draw any current that passes through it. If it had a resistance, it will decrease the amount of current flowing through the component, which would give inaccurate readings!

Hope you understood!
8. Does anybody have any good notes on drift velocity (other than the factsheet) or a good explanation theory on the topic?
9. (Original post by Nethmioysters)
voltmeters have "infinite" or high resistance, so that the current flowing will not be drawn by the voltmeter, but will pass through the component that is being measured (which is the main reason y v connect it in parallel)

An ammeter will have very low or zero resistance, so that it does not draw any current that passes through it. If it had a resistance, it will decrease the amount of current flowing through the component, which would give inaccurate readings!

Hope you understood!
hmm... Impressive answer... Thank you and good luck !
10. can someone explain the calculation part in the 13th question of unit 2 june 2014(R)
11. (Original post by Ahmed3651998)
hmm... Impressive answer... Thank you and good luck !
Thanks! good luck to you too!
12. can somebody explain what "plane includes direction of propogation" means?
does dis mean dat particles oscilate in planes which are perpedicular to direction of travel if so how?
13. wat is direction of energy transfer?
wen comsiderin polarised waves n oscilation
14. Propagation means direction of travel, so the plane in which light is polarized also includes the direction of propagation
15. In a wire I=nAvq. So as the temperature increases ( due to more collision of the electrons with the lattice, more energx is gained by the lattice,causing it to vibrate more). This decreases the drift velocity of the electrons,.
16. The person asking about 18 ciii June 2014. The are asking at what frequency will two strings be seen by the strobe lamp. So if the original frequency was 660Hz and the strobe lamp was set to measure that frequency, then if the frequency is doubled two strings will appear. This the max frequency cause if the frequency increases the positions of the antinodes will be different cause there will be more antinodes
17. (Original post by Dr.strange12)
In a wire I=nAvq. So as the temperature increases ( due to more collision of the electrons with the lattice, more energx is gained by the lattice,causing it to vibrate more). This decreases the drift velocity of the electrons,.
Nvm
18. Anyone has the unofficial markscheme?????????
19. How did everyone find this exam??
20. (Original post by fayella9)
Anyone has the unofficial markscheme?????????
I haven't found one, what did you get for the temperature question using the graph and what did you get for the length of wire?

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