Author Topic: Exam 2 Answer Thread (Read 6648 times) Tweet Share

Ahmad · « **Reply #30 on:** November 14, 2007, 01:36:02 pm »

For hydrogen question:

* Hydrogen is in space between Sun and Earth.
* As light passes through them some wavelengths corresponding to difference in energy levels are absorbed.
* Hence the other wavelengths are passed through.
* Note resemblance between emission spectrum of hydrogen and absorption.

Something on the lines of that, I wrote more.. but can't remember.

boulos90 · « **Reply #31 on:** November 14, 2007, 01:36:31 pm »

i got 1.1 for the one we had to read from the graph, that should be right, yeh?? :?

hifer · « **Reply #32 on:** November 14, 2007, 01:37:14 pm »

Quote from: "maxleng"

i said sunlight is missing the energy of hydrogen since it uses it, hence when passed through a prism the spectrum of hydrogen will not be seen

i dont think its totally right tho :?

I think it's coz the hydrogen in space n the atmosphere absorbs the wavelengths.. that's why they are missing in the spectrum we measure from the sun..

Wavelength in emission spectrums = wavelengths absorbed coz they correspond to the same energy

boulos90 · « **Reply #33 on:** November 14, 2007, 01:37:29 pm »

Quote from: "Ahmad"

For hydrogen question:

* Hydrogen is in space between Sun and Earth.
* As light passes through them some wavelengths corresponding to difference in energy levels are absorbed.
* Hence the other wavelengths are passed through.
* Note resemblance between emission spectrum of hydrogen and absorption.

Something on the lines of that, I wrote more.. but can't remember.

Meh, ill probably lose 1 mark for that 1, how much was it out of?

bilgia · « **Reply #34 on:** November 14, 2007, 01:45:02 pm »

Quote from: "Ahmad"

Yeah, so I got something like (can't remember very well):

2.5 A, 10 V, 2 V

6 W, 5 W, 5 W

PHEW.! i did pretty well

bilgia · « **Reply #35 on:** November 14, 2007, 01:45:39 pm »

Quote from: "boulos90"

i got 1.1 for the one we had to read from the graph, that should be right, yeh?? :?

i did that

___ · « **Reply #36 on:** November 14, 2007, 01:48:12 pm »

im pretty sure anywhere between 0.9 - 1.1 will be accepted..

i personally put 1.0

maxleng · « **Reply #37 on:** November 14, 2007, 01:48:45 pm »

it should be .9 b/c its a freq of 7.5 which is below 1... i really dont see how it can be 1.1 cos if u used the formula to work out the freq there is no way u can get over 1 (1 should be fine) but over it is pushing it. mainly because the line you drew matched up really well with the points.

if there tight they will not give you 1.1 (which they might be cos it was pretty easy) so i dont know...

what did people say for the last Qs on light

i had:

continous
discrete

filament: acc + dec of electrons (thermal excitation)
discharge tube: electrons excited then drop down releasing energy = light

Ahmad · « **Reply #38 on:** November 14, 2007, 01:50:29 pm »

I put 1.0, looked about that on my graph. And yes, I pretty much said what you did for the light questions.

AkirA · « **Reply #39 on:** November 14, 2007, 01:52:52 pm »

I agree with Ahmad.

bilgia · « **Reply #40 on:** November 14, 2007, 01:53:52 pm »

damn lost at least 3marks so far

avogarbro · « **Reply #41 on:** November 14, 2007, 02:03:52 pm »

Ahmad, your answers look similar to mine. (but im not certain) i remember considering a voltage drop in my power line question.

Vdrop was like 4 *.5 = 2 V drop across the power lines wasn't it?

maxleng · « **Reply #42 on:** November 14, 2007, 02:04:19 pm »

Quote from: "avogarbro"

Ahmad, your answers look similar to mine. (but im not certain) i remember considering a voltage drop in my power line question.

Vdrop was like 4 *.5 = 2 V drop across the power lines wasn't it?

i got that

mtyp · « **Reply #43 on:** November 14, 2007, 02:06:24 pm »

what was the answer to the induced current thing? about current flowing momentarily/continuously from X to Y / Y to X?

avogarbro · « **Reply #44 on:** November 14, 2007, 02:07:48 pm »

According to that the voltage at the end of the powerlines (where the transformer was) should be 10V (12V-2V) . I remember the transformer ratio was like 5:1 (primary to secondary). So at the globe the voltage was 2V.

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