Re: EXAM!!!!!!!!!!!!

Admin · Admin on Mon May 25, 2009 5:00 pm

I have to be in clydebank high tomorrow morning from 9 am. However I intend to be in school from 8 am. I am on the phone to Mr. Allan just now and he will be available all morning.

S.McGrath · S.McGrath on Mon May 25, 2009 5:22 pm

okayyy thanks

what is the percentage you need to get an A, B or C in the exam?

2007: Q28b iii
Q27 b ii

2008: 24 b, 25 b ii, 26 b, 27a ii & b, 28 a, and 29 b

as you can probably guess, last years paper caused me a couple of promlems Laughing

Connor Einstein · Connor Einstein on Mon May 25, 2009 5:42 pm

for 25Bii the voltage is 3.4 v so V=IR so R=3.4/1.6x10^-3

Connor Einstein · Connor Einstein on Mon May 25, 2009 5:51 pm

26bi is v1=vsR1/R1+R2
12*14/2+1.2
7.5

Suzy · Suzy on Mon May 25, 2009 5:58 pm

Aw right! I get the gold leaf part Smile

thank you

When you say the diode points to positive terminal, is that the pointy bit of the triangle???
And the point of the triangle is always meeting the line of the diode??

I tried drwaing a picture but how do i upload it???

Suzy · Suzy on Mon May 25, 2009 6:03 pm

Anyone know how to do 2005 question 27 b ii ????
I keep getting 2.23 x 10^-5 degrees instead of 23!!! Evil or Very Mad

S.McGrath · S.McGrath on Mon May 25, 2009 6:08 pm

sorry connor i mean 25 b iii

Admin · Admin on Mon May 25, 2009 6:12 pm

Right all I am going to answer you all over several messages as I have a driver conflict right now that caused my machine to crash towards the end aof a long message not too happy about that as I lost all the work.
A = 70 %
B = 60 %
C = 50 %

Admin · Admin on Mon May 25, 2009 6:15 pm

Both Connor's answers are right. Well done.
2007 Q27.b.ii. As Rt increases, P.d. Q decreases, inverting input decreases, Vout increases transistor switches L.E.D. on.

Admin · Admin on Mon May 25, 2009 6:20 pm

2007 28 b iii. n x wavelength = d sin(00,
n = 2, d = 4.00 x 10 ^ -6, sino = opp / hyp = BC/AB
plug these in and wavelength = 4.91 x 10 ^-7 m,
the error bit, take your largest % error which is the error of BC of 3.7 %, find 3.7 % of wavelength = 0.18 x 10^-7
final answer 4.91 x 10^-7 +/- 0.18 x 10^-7 m

Admin · Admin on Mon May 25, 2009 6:22 pm

2008 24 b E = I(R + r), E and R constant, r decreases so I must increase, P = I^2 R, R constant and I increases : P must increase

Admin · Admin on Mon May 25, 2009 6:26 pm

2008 25 b iii E = 1/2 CV^2
E = 10.8 x 10 ^-3, C = ? , V^2 = 144
C = 2E/V^2 = 0.00015 F

Admin · Admin on Mon May 25, 2009 6:32 pm

SUZY PLEASE READ ANSWER AND LOOK AT QUESTION 26 2008 PAPER IT WILL ANSWER YOUR DIODE QUERRY
2008 26 b ii Vo = (140 / 20) x (7.2 - 7.5) = 7 x - 0.3 = -2.1V
2008 26 b iii Yellow diode, it is pointing to the lower potential i.e. -2.1 is less than 0, if the output had been 2.1 then the blue led would light up.

Suzy · Suzy on Mon May 25, 2009 6:40 pm

Aaww right okay - I understand Smile

...though really hope it doesnt come up tomorrow pale

lol

And see that question, its really similar to one in 2005, Q27 part b ii

Do you have to split the circuit up in some way???

Admin · Admin on Mon May 25, 2009 6:46 pm

2008 27 a ii use v = f x wavelength to find wavelength in air = 6.25 x 10^-7m, then n = wavelength air / wavelength glass so
wavelength glass = wavelength air / n = 3.88 x 10 ^-7m.
2008 27 b blue light refracts more than red light so the refractive index for blue light is higher, the light bends more so it passes through x.