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diode and capacitor

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saeedali

New Member
hello.

please see the following circuit and tell that if the diode will be failed or not and why?
what is main cause of failing of electronic components?(over current or overvoltage or power dissipation?)
suppose that i connect a ceramic capacitor 100nf/50v instead of the diode.
will the capacitor be failed?why?
upload_2013-12-9_11-45-57.png

best regards.
 

large_ghostman

Well-Known Member
Most Helpful Member
if you want to put 300V through a 50V cap then the answer to your question what is the main reason for failure i would say stupidity :D
and there are two diodes which do you mean?
 

ronsimpson

Well-Known Member
Most Helpful Member
This sounds like homework.
When the voltage source goes positive it will change C up to ________voltage. You will in the blank. ( not 300V)
When the voltage source goes negative it will go to a negative ___________volts at the peak. Fill in the blank.
How many volts are across the 1N4007 (maximum point)? What is the diode rated for?
The 1N4001 is a 50 volt cap. Good for it that there is a resistor to limit the current!
 

large_ghostman

Well-Known Member
Most Helpful Member
i tried to sim this but i dont think i got it right :( still when op answers i will say what i got
 

saeedali

New Member
thanks for your replies.

reverse voltage of 1n4007 is 1000volt and it isn't failed at all but 1n4001 has 50 volt reverse voltage.
i assembled this circuit on a breadboard and expect the diode 1n4001 failed but it wasn't.
my main question is that why wasn't the diode 1n4001 failed?
beat regards.
 

ronsimpson

Well-Known Member
Most Helpful Member
Because there is a 150k resistor that limits the current flow. The watts are so low that the part does not heat up and die.
Over voltage is not good. The parts might die or they might survive if the current is very low.
 

saeedali

New Member
how much is power dissipation of the 1n4001 in this situation(reverse biased)?
how much current can the diode withstand in reverse bias before failing?
what is main cause of failure of electronic components?overvoltage overcurrent or power dissipation?
does capacitor have watt parameter?(why wasn't capacitor failed?)

thanks.
 

ronsimpson

Well-Known Member
Most Helpful Member
i am waiting for your replies.
Sorry I have nothing to do all day but respond.
how much is power dissipation of the 1n4001 in this situation(reverse biased)?
how much current can the diode withstand in reverse bias before failing?
The part is rated for most of one watt. With 50 volts you can find how much current that is.
When you use parts out side their normal rating there is no way to know what will happen.
If the part 'breaks down' nicely it can handle 1W but the part may only break down in a very small part of the die and that small part can not take 1 watt. So it could over heat with a very small amount of power. This is not tested. No one knows.
what is main cause of failure of electronic components?overvoltage overcurrent or power dissipation?
Your teacher will say.....what he wants you to answer.
.....over current leads to over power.
.....over voltage (probably) will lead to over power. The over power might be in only a very small corner of the part.
.........over dissipation will kill the part.
.....Tell your teacher a hammer works every time.
does capacitor have watt parameter?(why wasn't capacitor failed?)
The capacitor might fail in 1nS or 1mS or 1S or 1 week or any time. The next cap you test will be different. There is no knowing. The part will work from -50V to +50V and more than that why knows. There is no rating when it will fail just where it will not fail.
Most capacitors do not have a power rating. Very high current caps do but that is very complicated to explain.
 
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