Engineering Thread

Jonathan

TheAmateur wrote: »

Did a bit of creative googling and managed to find this thread from this very website, by an engineering student from trinity (afaik, I mean the experiment is identical). He seems to have actually had to do part 4 properly, but he doesn't explain how to predict the phase angles...

It is a trinity student. Someone who still posts to this day.

Boston

I posted that. Well done stalker jmccrohan. Basically we were told "If it looks like this, its out of phase by this much" and so on. See here for what values you should use .

TheAmateur

So the one I have is out of phase by pi radians, which is the max phase angle... that must've been what I was trying to tell myself with max alpha = pi...
Would I be right in saying then that at a frequency of 500Hz, a capacitance of 0.1 x 10^-6 farad and a resistance of 1k ohm, we can predict that the waves should be out of phase by pi radians, and then the oscilloscope verifies this?

Boston

There's a formula to determine the equivalent impedance and associated phase. For a pure RC circuit the phase should be -90 degree from memory. The idea would be to use the formulae to estimate the phase and then use the scope to confirm.

Brian

TheAmateur wrote: »

WOW! 800! Hey isn't that longer than the 1500 word assignment you did? :P

Yeah. Also, Boston's lab report was 1500 words. Variable capacitance must've really gotten him excited.

TheAmateur

Boston wrote: »

There's a formula to determine the equivalent impedance and associated phase. For a pure RC circuit the phase should be -90 degree from memory. The idea would be to use the formulae to estimate the phase and then use the scope to confirm.

Oh man I bet Prof. Fannin has done it with us an all... there's. just. so. much. 1E6! I'm not looking forward to that exam. Shame about him retiring too, he's pretty cool/crazy.

Brian

Not to mention irritating, <libellous, and <more libellous>.

Brian

Hey, Boston, this is your kinda thing isn't it?

http://www.engadgetmobile.com/2009/04/11/3gpp-publishes-worlds-first-femtocell-standard/

Boston

Yep.

Brian

Is there any conclusive proof that cellphone radiation is more hazardous than a wifi router?

Boston

Cellphones typically radiate at a power far less then wifi routers (1W).

Brian

Even a femtocell router?

Boston

125mW typically.

Brian

What's the diameter of the throwing arm?

TheAmateur

Baza210 wrote: »

What's the diameter of the throwing arm?

28mm

Brian

TheAmateur wrote: »

28mm

Cheers. Didn't realise that the webCT deadline was at 12 noon. Oh well, it's Summer.

Brian

Lectures not cancelled for EMS day

Fukken lold

Unregistered.

Baza210 wrote: »

Fukken lold

I wonder how many people out in the rain right now AND missing lectures for the privilage

Brian

The things you miss out on when you click Report Spam for all official looking emails..

Jonathan

Baza210 wrote: »

The things you miss out on when you click Report Spam for all official looking emails..

How come I didn't get that email?

Brian

701 != 702, eh?

mathew

jmccrohan wrote: »

How come I didn't get that email?

It was probably from the Dept.. since we dont have lectures.. we didnt get it..

devinejay

Anyone else find trying to solve this week's C++ using recursion seems overly complicated.

Read; I got it working with old school for and if loops, but I can't for the life of me figure out how to do with recursion.

Jonathan

devinejay wrote: »

Anyone else find trying to solve this week's C++ using recursion seems overly complicated.

Read; I got it working with old school for and if loops, but I can't for the life of me figure out how to do with recursion.

Which one is it?

devinejay

Write a recursive function to sort an array of doubles into ascending order
using the following idea: Swap the largest element into the last position, then
sort the rest of the array by a recursive call.
Embed your function in a program which reads a sequence of doubles from
the user, terminated by -9999, and outputs the sorted sequence.

Well?

Boston

int index_of_largest(int unsorted_a_int*,int size)
{
if(size==1)
return 0;

index = index_of_largest(a,size-1);
if a[size] > a[index]);

return size;
else
return index;

}

Jonathan

devinejay wrote: »

Well?

Assume double array[20];

One way to do it would be to search array from 0 to 19, find the biggest number, swap it to the last slot. Repeat 0 to 18, repeat 0 to 17 etc.

devinejay

Yeah I'll give it a try, I have what you described done but I can't manage it with recursion yet.

Boston, does not not simply return the index of largest using recursion but not actually do any sorting?

Boston

Erm, finding the index of the largest is the hard bit.

devinejay

Oh right, well if that's the case I'm just gonna leave it and come back to it in a day or so, have a fresh go at it and see if I can spot what I'm missing now.

Thanks.


Edit; True enough, it got it when I left it and came back to it. It's annoying the way you can end up trying for ages to solve the problem, when a fresh approach is all you need. It's not going to be possible to do that in the exam!