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Author Topic: Enterance exam question  (Read 1448 times)

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Offline eripahaTopic starter

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Enterance exam question
« on: May 18, 2016, 02:24:57 pm »
I did a entrance exam that had following question. Calculate Vcc when VL=6.5volts,  R1 = 2k, R2 =4k, RL 650, c1 = 3.2mF. Circuit has been powered up for a long time.

they some how get over 20volts.... wtf is going on?




What they got
« Last Edit: May 18, 2016, 02:26:49 pm by eripaha »
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Offline Skimask

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Re: Enterance exam question
« Reply #1 on: May 18, 2016, 02:34:05 pm »
And?
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I didn't take it apart.
I turned it on.

The only stupid question is, well, most of them...

Save a fuse...Blow an electrician.
 

Offline Ian.M

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Re: Enterance exam question
« Reply #2 on: May 18, 2016, 02:40:49 pm »
Treating it as a potential divider gives a divider ratio of  0.65/(0.65+4/3) or 0.3277.   Multiplying by the result above (before rounding) gives 6.5V.   So yes, fractionally under 20V is the correct answer.
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Offline Jeroen3

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Re: Enterance exam question
« Reply #3 on: May 18, 2016, 02:52:00 pm »
The decoy capacitor surely put people on the wrong track.
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