School/Uni Help Thread

I honestly think they'll mark you for making the effort despite clearly not having the luck of the questions falling the right way Good luck mate

 

Psychology is a terrible subject, did it for 12 weeks and never doing it again thankfully

 

Spot on, beat me to it

 

My results aren't matching up

Theoretically I had myself down as getting 105 for Power dissipation


IT = VS/RT
= 5/238.03
= 0.021A
= 21mA

PD = (IT^2)/Vs
= (0.021^2)/5
= 0.000882

 

...aye

 

Anyone done higher photography? I've picked it and wanted to see if anyone knows what's involved apart from learning to take pictures. haha

 

How the * is that a subject?

 

Dunno looked interesting and unique and I couldn't pick anything else in the column.

 

Got my international security exam on Monday. Anyone else taken something similar? My first of 5 exams, after which I'll be done at Uni!

 

My thoughts exactly but hey lots of money to be made in film and photography, seeing as it's the digital age and all....

As for the guy that asked - I've no idea as I haven't done it but see here as it should tell you what you'll be studying: http://www.sqa.org.uk/sqa/files_ccc/H_PhotographyArrangements.pdf

 

Is this real!

 

I finished uni on Wednesday, dissertation submitted and all. So * stressful.

 

Yes, the year coming is the first it started.

 

Need a bit of help with this, I asked previously and managed to get so far with this. It's to be included in a report which is due this week



Using the nominal values of 100, 200, 300 and 400 Ohms, calculate:

Parallel resistances RP1 and RP2
Total circuit resistance RT
Total Current IT
Component voltages VP1 and VP2
Branch currents IA, IB, IC, and ID
Total Power Dissipated PD

I got so far but could not calculate the branch currents or total power disspated

My calculations:

RP1 = (RA*RB) / (RA+RB)
= (100*200) / (100+200)
= 66.6

RP2 = (RC*RD) / (RC+RD)
= (300*400) / (300+400)
= 171.43

RT = RP1+RP2
= 66.6 + 171.43
= 238.03

IT = VS/RT
= 5/238.03
= 0.021A
= 21mA

VP1 = VS * (RP1 / (RP1+RP2))
= 5 * (66.6 / (66.6+171.43))
= 1.4V

VP2 = VS * (RP2 / (RP1+RP2))
= 5 * (171.43 / (66.6+171.43))
= 3.6V

Just cannot calculate branch currents (IA, IB, IC, ID) and Power dissipated

 

The current that goes across branch AB is found by:

IAB=IT*(RP2/(RP1+RP2))
IAB=21*(171.43/(171.43+66.6))
IAB=15.12mA
​

Now this is the current across the branch with the A and B resistors in it, and we use this to work as IA and IB.

IA=IAB*(RB/(RA+RB))
IA=15.12*(200/(200+100))
IA=10.08mA

IB=IAB*(RA/(RA+RB))
IB=15.12*(100/(100+200))
IB=5.04mA
​

Now we do this again for the other parallel branch, first finding the current ICD:

ICD=IT*(RP1/(RP1+RP2))
ICD=21*(66.6/(66.6+171.43))
ICD=5.87mA

​

And now use this to calculate IC and ID as follows:

IC=ICD*(RD/(RD+RC)
IC=5.87*(400/(400+300))
IC=3.354mA

ID=ICD*(RC/(RC+RD))
ID=5.87*(300/(300+400))
ID=2.516mA

​

Then to get the Power dissipated you can do:

PD=IT*VS
PD=(20mA)*5
PD=0.105W

or you can do it this way but it gives the same answer

PD=(VT^2)/RT
PD=(5^2)/238.03
PD=25/238.03
PD=0.105W
​

There you go man stuck the numbers in aswell

​

 

You are a godsend mate really appreciate that, and good luck with your test on Wednesday! :thumbup:

 

what the absolute * did I just read?

 

Totally agree with this, was just about to post this myself tbh. Obvious answer anyway.

 

A Level Quantum Physics exam at 9 tomorrow... * help me.