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Anonymous Poster

leakage resistance calculation

05/15/2009 5:52 PM

Hello there i hope somone one can help me with this question i have, i am doing an open learning course and this question has me stumped

A 100pf capacitor with mica dielectric of relative permittivity 12 and resistivity of 10power14 Ohms/metre has a leakage resistance of ?.

calculate the leakage resistance.

now all my formulas relate to area and thickness or length but im stumped at how to use the information given

any help appreciated

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#1

Re: leakage resistance calculation

05/15/2009 7:29 PM
  1. Use capacitance & dielectric relative permittivity to find A/d (plate area / separation)
  2. Plug result into relationship between resistance, resistivity & A/d

The formulae are easily found from your textbook, or by searching "relative permittivity" and "resistivity" in Wikipedia.

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#3
In reply to #1

Re: leakage resistance calculation

05/18/2009 5:53 PM

Aren't you just ENABLING this guy by doing his work, and even pointing out how EASY it was ? Why do you bother? Great answer , by the way (which is why I chose to respond). I knew it was an area calculation.

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#4
In reply to #3

Re: leakage resistance calculation

05/18/2009 6:45 PM

"Aren't you just ENABLING this guy by doing his work, and even pointing out how EASY it was?"

Yes.

"Why do you bother?"

I'm just such a nice kinda guy .

More seriously, I generally ignore homework questions (or tell 'em to read the book/google it/ask Teach), unless I get the feeling that they've at least thought about the problem (that's how this one came across to me, at the time). Time was (early days of me in CR4) I'd do the whole thing, showing all the steps along the way, but I've realized that this was just an ego-trip and helped no-one.

On this one, I'd've liked to have spent a bit more time pointing in the right direction without giving too much away (I think I probably made it too easy - "Its an area calculation" type hints would've been better), but I was pressed for time (that's my story & I'm sticking to it!).

If someone has a "real world" (i.e. not homework) problem, and I can help, I'll generally fall over myself trying.

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#5
In reply to #4

Re: leakage resistance calculation

05/19/2009 10:39 AM

We've all been occasionally blinded and cannot see the tree in the forest. I feel you answered the question admirably. A single hint followed by waiting for the student to grasp the thread works great in a student mentor relationship. Here you identified the path in terms he should remember and apply to similar questions in the future. But the student had to understand the meaning of the path description and then walk that path to get the answer.

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#2

Re: leakage resistance calculation

05/18/2009 9:55 AM

Bravo Guest,

You've posted a homework problem in precisely the correct format to be answered. You stated that it's a homework problem and then stated the problem. You next stated both an understanding of what was requested and why the information given appeared inadequate to answer. As long as you continue to ask for guidance to solve your homework, instead of asking people to solve your homework, you will get help here.

P.S. Get yourself a handle, please.

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