Login

Search the forums now!

Welcome, Guest. Please login or register.

December 06, 2025, 03:39:33 am
Pages: 1 2 [3]   Go Down

Author Topic: umep physics thread  (Read 10089 times)  Share 

0 Members and 1 Guest are viewing this topic.

/0

  • Victorian
  • ATAR Notes Legend
  • *******
  • Posts: 4124
  • Respect: +45
Re: umep physics thread
« Reply #30 on: September 14, 2009, 01:41:25 am »
0
Is it possible to charge up a capacitor in a circuit without a resistor? What would happen to the time constant?
Logged

/0

  • Victorian
  • ATAR Notes Legend
  • *******
  • Posts: 4124
  • Respect: +45
Re: umep physics thread
« Reply #31 on: January 11, 2010, 08:38:16 pm »
0
Ah well, umep may be over but I still have questions :D

Say you have a charge distribution in the picture, and you want to find the potential THEN the electric field at P, using

I found the potential to be 0, and yet the field isn't. Why is this?


Thnx :)
« Last Edit: January 11, 2010, 08:41:18 pm by /0 »
Logged

kamil9876

  • Victorian
  • Part of the furniture
  • *****
  • Posts: 1943
  • Respect: +109
Re: umep physics thread
« Reply #32 on: January 12, 2010, 01:26:14 pm »
0
How did you work out ?
Logged
Voltaire: "There is an astonishing imagination even in the science of mathematics ... We repeat, there is far more imagination in the head of Archimedes than in that of Homer."

/0

  • Victorian
  • ATAR Notes Legend
  • *******
  • Posts: 4124
  • Respect: +45
Re: umep physics thread
« Reply #33 on: January 12, 2010, 09:02:53 pm »
0
I just used



(reference point at infinity)
Logged

kamil9876

  • Victorian
  • Part of the furniture
  • *****
  • Posts: 1943
  • Respect: +109
Re: umep physics thread
« Reply #34 on: January 12, 2010, 11:21:00 pm »
0
The problem is you worked out V at a single point, rather than as a function in terms of and . (e.g: say for simplicity z=0 so we have a one dimensional case, then you have
But V=0 at x=a, does not imply the derivative at x=a is 0
Logged
Voltaire: "There is an astonishing imagination even in the science of mathematics ... We repeat, there is far more imagination in the head of Archimedes than in that of Homer."

/0

  • Victorian
  • ATAR Notes Legend
  • *******
  • Posts: 4124
  • Respect: +45
Re: umep physics thread
« Reply #35 on: January 12, 2010, 11:36:48 pm »
0
ah i understand, thanks kamil :)
Logged

TrueTears

  • TT
  • Honorary Moderator
  • Great Wonder of ATAR Notes
  • *******
  • Posts: 16363
  • Respect: +667
Re: umep physics thread
« Reply #36 on: January 12, 2010, 11:37:57 pm »
0
Quote from: /0 on January 12, 2010, 11:36:48 pm
ah i understand, thanks kamil :)
THA...
Logged
PhD @ MIT (Economics).

Interested in asset pricing, econometrics, and social choice theory.

/0

  • Victorian
  • ATAR Notes Legend
  • *******
  • Posts: 4124
  • Respect: +45
Re: umep physics thread
« Reply #37 on: January 12, 2010, 11:40:08 pm »
0
Logged

kamil9876

  • Victorian
  • Part of the furniture
  • *****
  • Posts: 1943
  • Respect: +109
Re: umep physics thread
« Reply #38 on: January 13, 2010, 12:11:11 am »
0
wtf?
Logged
Voltaire: "There is an astonishing imagination even in the science of mathematics ... We repeat, there is far more imagination in the head of Archimedes than in that of Homer."

TrueTears

  • TT
  • Honorary Moderator
  • Great Wonder of ATAR Notes
  • *******
  • Posts: 16363
  • Respect: +667
Re: umep physics thread
« Reply #39 on: January 13, 2010, 12:14:46 am »
0
.
Logged
PhD @ MIT (Economics).

Interested in asset pricing, econometrics, and social choice theory.

/0

  • Victorian
  • ATAR Notes Legend
  • *******
  • Posts: 4124
  • Respect: +45
Re: umep physics thread
« Reply #40 on: January 13, 2010, 07:01:12 pm »
0
Quote from: kamil9876 on January 13, 2010, 12:11:11 am
wtf?

it's a code
TT posted a hint :P



"A conical surface (an empty ice-cream cone) carries a uniform surface charge . The height of the cone is h, as is the radius of the top. Find the potential at the centre of the top, taking the reference point as infinity."

Can I just see the answers people get for this? Mine differs from the book's and I can't find anything wrong with mine.
 
thanks!
« Last Edit: January 13, 2010, 07:09:23 pm by /0 »
Logged

kamil9876

  • Victorian
  • Part of the furniture
  • *****
  • Posts: 1943
  • Respect: +109
Re: umep physics thread
« Reply #41 on: January 15, 2010, 12:15:38 am »
0
Draw an line-axis on the surface of the cone (0 is at the tip of the cone). Call this the axis.

Now the surface area of a cone is and we know from similair triangles that . Differentiating gives:

(ie the area of a strip of a cone).


The distance from any point on this strip to the point of interest is .

Now to actually do some electromag:



And now integrate (good luck).


Logged
Voltaire: "There is an astonishing imagination even in the science of mathematics ... We repeat, there is far more imagination in the head of Archimedes than in that of Homer."

/0

  • Victorian
  • ATAR Notes Legend
  • *******
  • Posts: 4124
  • Respect: +45
Re: umep physics thread
« Reply #42 on: January 15, 2010, 12:33:02 am »
0
thx kamil :)
Logged
Pages: 1 2 [3]   Go Up