June 2011 G485-Fields, Particles and Frontiers of Physics Watch

ChoYunEL
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#181
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#181
(Original post by jam.wa)
There is SO MUCH PHYSICS!
Dream question:

'Fail to calculate this really difficult capacitor question'

I HATE capacitors more than anything.
Can you do resistors? I like to look at Capacitors like resistors even though they're not
V=IR and Q=VC
In Series or a resistor is a parrallel for a capacitor
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M_I
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#182
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#182
(Original post by Right Guard 3.D)
The electrons travel through more volts so the eV (electron volts) increases.

An electron volt is a standard unit of energy meaning it can make eV= 1/2 mv^2 so increasing the voltake increases eV and increases KE
Genius! Thanks.....I just realised what an eV is haha.
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jam.wa
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#183
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#183
(Original post by ChoYunEL)
Can you do resistors? I like to look at Capacitors like resistors even though they're not
V=IR and Q=VC
In Series or a resistor is a parrallel for a capacitor
I understand the basics, it's just when they plonk two switches on, say one's open, one's closed, then both closed and then blahdeblahdeblah.
Having said that I just finished doing June 2010 and didn't do too bad in the end
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M_I
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#184
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#184
In the specimen paper, question 8.d)i) why do the multiply by 100?
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sulexk
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#185
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#185
Why is the film in an intensifying screen sandwiched between two phosphor screens, what is the point of the second one, and what impact does this have on the resulting image produced?
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InsaneFandom
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#186
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#186
Could someone please show me how you rearrange V=Voe^-t/CR to get t? :/
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Oh my Ms. Coffey
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#187
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#187
(Original post by InsaneFandom)
Could someone please show me how you rearrange V=Voe^-t/CR to get t? :/
V/Vo = e^-t/CR

ln(v/vo) = -t/CR

ln(v/vo)x-CR = t
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CoffeeStinks
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#188
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#188
Guys how does x ray diffraction provide evidence for the atomic radius being around 10^-10?

Please help.
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Summerdays
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#189
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#189
(Original post by Right Guard 3.D)
The electrons travel through more volts so the eV (electron volts) increases.

An electron volt is a standard unit of energy meaning it can make eV= 1/2 mv^2 so increasing the voltake increases eV and increases KE
Yes. Loss of electrical potential energy (qV) = Gain of kinetic energy.
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jam.wa
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#190
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#190
(Original post by CoffeeStinks)
Guys how does x ray diffraction provide evidence for the atomic radius being around 10^-10?

Please help.
Are you doing an old paper?
I'd probably start off with that equation from AS n(lambda)=dsin(theta)
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sulexk
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#191
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#191
I have been going through the june 2010 and jan 2011 paper, just looking over content, and so far for radioactivity, the smoke detector has not come up yet- so it is a possibility. In jan 2011 carbon dating had come up and in june 2010 half life came up. So perhaps the smoke detector will come up. Its a possibility. So here is how the smoke detector works:

The alpha particles are detected by an electronic circuit
When smoke enters the device the alpha particles are absorbed
and the current in the circuit reduces significantly and the circuit then triggers the alarm.

Note- alpha radiation is used because it is the most strongly ionising and therefore the most likely to be absorbed by the smoke particles. As well as this the range of alphar particles is so small that they're unlikely to constitute a hazard to the user.

Hope this helps.

Thank you
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sulexk
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#192
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#192
(Original post by sulexk)
Why is the film in an intensifying screen sandwiched between two phosphor screens, what is the point of the second one, and what impact does this have on the resulting image produced?
Any ideas?
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Right Guard 3.D
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#193
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#193
(Original post by Oh my Ms. Coffey)
V/Vo = e^-t/CR

ln(v/vo) = -t/CR

ln(v/vo)x-CR = t
What does the x in the last line represent please? And I repped you since you firmed my understanding onhow to rearrange exponentials

(Original post by Summerdays)
Yes. Loss of electrical potential energy (qV) = Gain of kinetic energy.
Loss=gain? Doesn't that go against the law of conversation of energy? If energy is gained by an electron, wouldn't it also gain kinetic as the energies are 'like one'? Or am I getting confused?
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jam.wa
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#194
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#194
(Original post by sulexk)
Any ideas?
I think the first phosphor screen absorbs X-ray photons and re-emits visible light photons. If I had to guess, I'd say the second one did more or less the same. The resulting image would be darker, because the film is more sensitive to visible light photons. So the image would appear crisper.
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Summerdays
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#195
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#195
(Original post by Right Guard 3.D)



Loss=gain? Doesn't that go against the law of conversation of energy? If energy is gained by an electron, wouldn't it also gain kinetic as the energies are 'like one'? Or am I getting confused?
No, this IS the conservation of energy. Originally the electron had energy qV. As the electron is repelled from another electron, as it moves away from the otehr electron its potential energy (qV) is turned into kinetic energy. So energy is conerved. The electron gains maximum kinetic energy once the potential difference is zero (i.e.: once the electron is essentially an inifite distance away from the other electron.)
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Right Guard 3.D
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#196
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#196
(Original post by sulexk)
Why is the film in an intensifying screen sandwiched between two phosphor screens, what is the point of the second one, and what impact does this have on the resulting image produced?
My book (Physics 2 for OCR A by Cambridge university press) doesn't show that it is sandwiched, it just has the phosphor screen and then the photocathode which elections are enjoyed from via the photoelectric effect. So id say there isn't really a point of the second one? Since the main focus are the elections emitted which then get accelerated to the anode?
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CoffeeStinks
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#197
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#197
(Original post by jam.wa)
Are you doing an old paper?
I'd probably start off with that equation from AS n(lambda)=dsin(theta)
Yes it's Jan03. It doesn't directly relate to the new past papers but I'm trying to cover as many aspects. Just incase they want to go off on a tangent in the actual exam.

Thanks.
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Right Guard 3.D
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#198
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#198
(Original post by Summerdays)
No, this IS the conservation of energy. Originally the electron had energy qV. As the electron is repelled from another electron, as it moves away from the otehr electron its potential energy (qV) is turned into kinetic energy. So energy is conerved. The electron gains maximum kinetic energy once the potential difference is zero (i.e.: once the electron is essentially an inifite distance away from the other electron.)
Now you said that, you were absolutely correct and I am annoyed for asking what I did :L

Thanks for clearing that up!
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Oh my Ms. Coffey
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#199
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#199
(Original post by Right Guard 3.D)
What does the x in the last line represent please? And I repped you since you firmed my understanding onhow to rearrange exponentials



Loss=gain? Doesn't that go against the law of conversation of energy? If energy is gained by an electron, wouldn't it also gain kinetic as the energies are 'like one'? Or am I getting confused?
Multiply, I just kept it in there to show you multiply not divide.
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Ralphus J
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#200
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#200
What does it mean by "describe the principles of ultrasound scanning"?? its on the specification sheet (OCR Physics A) under ultrasound (d). Please reply as soon as possible

Thanks
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