Calling electronics whizs (solved) 

"bob and john" (bobandjohn) 11/10/2015 at 18:56 • Filed to: None

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need help with a homework question (its simple...but my brain is fried and its due tonight....)

Question: A 10mF capacitor is charged to 210 volts before the voltage supply becomes disconnected (eg. The instrument’s power was turned off). The capacitor discharges through a 10 mega-ohm resistance. How long does it take for the capacitor to reach the ‘safe’ voltage of 24V?

drifting Tesla for your time


was looking at one formula wrong. oops

My citroen won't start > bob and john 11/10/2015 at 19:04

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2.6 millipumpernickels squared

davedave1111 > bob and john 11/10/2015 at 19:07

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http://www.daycounter.com/Calculators/Ca…

Mr. Ontop, No Strokes, No Smokes...Goes Fast. > My citroen won't start 11/10/2015 at 19:15

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I thought it was 1.21 gigawatts.

My citroen won't start > Mr. Ontop, No Strokes, No Smokes...Goes Fast. 11/10/2015 at 19:17

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The question is how long you silly goose, it needs to be a measure of time.

Phyrxes once again has a wagon! > bob and john 11/10/2015 at 19:22

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The calculator below should give you the right answer but I assume you would like to know how it works.

Warning math ahead (disclaimer: I am a AP Physics Teacher)

Not my powerpoint but similar to the one I use, in other news Kinja and Drive don’t play nice so I grabbed one from google.

Calculus explanation for charging and discharging

If you don’t care about calculus, I don’t this is why I’m not an EE.

This website will give you an algebraic answer

Mr. Ontop, No Strokes, No Smokes...Goes Fast. > My citroen won't start 11/10/2015 at 19:22

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Oh well then, a waffel! Because motorcycles don’t need windshield wipers.

Highlander-Datsuns are Forever > bob and john 11/10/2015 at 19:23

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where F=farad, A= ampere , V= volt , C= coulomb , J= joule , m= metre , N= newton , s= second , W= watt , kg= kilogram , = ohm , H= henry .

One of these or a combination should do the trick.

bob and john > Highlander-Datsuns are Forever 11/10/2015 at 19:26

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...that looks mildly concerning. but I got figured out

My citroen won't start > Mr. Ontop, No Strokes, No Smokes...Goes Fast. 11/10/2015 at 19:28

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But only if the Cup-Noodles are chicken flavoured

Highlander-Datsuns are Forever > bob and john 11/10/2015 at 19:32

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Argon walks into a bar, the bartender says we don’t serve noble gasses here. Argon doesn’t react.

Mr. Ontop, No Strokes, No Smokes...Goes Fast. > My citroen won't start 11/10/2015 at 19:33

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Then we are in agreement.

webmonkees > bob and john 11/10/2015 at 19:46

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or,

   ××ln10