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Comments on Voltage and Current of capacitor

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Voltage and Current of capacitor

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How do I find the voltage of the capacitor and the current through the capacitor after the switch is closed?

hi

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1 comment thread

Much better schematic, +1. (1 comment)
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After the switch is closed:

hi

The general formula for finding the voltage of the capacitor is:

hi

where Vf is the voltage of the inductor after infinite time,Vo is the voltage of the capacitor at the time the switch is closed

Because capacitors resist any change in voltage

hi

This tells us that at the moment the switch is closed the voltage of the capacitor will be equal to its voltage before the switch is closed whichcis equal to 0.

hi

As t tends to infinity the inductor will act as a open circuit which means that by voltage division the voltage will be 0.88V

the R in the exponent is the total resistance seen by the capacitor which is:

hi

so the voltage of the capacitor equation will be:

hi

and the current through the capacitor will be:

hi

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3 comment threads

SI Unit symbols vs. variables (3 comments)
Sloppiness with units not tolerated here! (5 comments)
You need to do some proofreading. (3 comments)
Sloppiness with units not tolerated here!
Olin Lathrop‭ wrote over 3 years ago

I've said this before, so this time you get a -1 right away. We do engineering here, where units are important. Every numeric value that is not dimensionless must be shown with its unit. Units must match on opposite sides of every equals sign. If not, the equation is wrong, just like if the numeric values didn't match.

For example, you show 2(4/9), which is dimensionless quantity, and equate that to 0.88 V. Nothing with units of volts can every be equal to a dimensionless quantity. If I were marking homework like this, it would be wrong. If your professors are letting you get away with this kind of sloppiness, then they aren't real engineers, and aren't doing you any favors.

There is no excuse. Don't be so lazy. Consider it a requirement for now until you grow up enough to realize it's important for yourself.

Ping me when you fix all the units issues, and I'll undo the -1.

MissMulan‭ wrote over 3 years ago

The (missing)units are obvious if you read the post.

Olin Lathrop‭ wrote over 3 years ago

Whether one can guess the units is not the point. It's still just plain wrong to equate a value of Volts to a dimensionless quantity.

MissMulan‭ wrote over 3 years ago

It isn't dimensionless im just doing the math.

Olin Lathrop‭ wrote over 3 years ago

No, 2(4/9) is dimensionless. That's what you wrote.