0
\$\begingroup\$

I was watching a lecture on State Variables on YouTube here

The professor mentioned that "if three capacitors form a loop, the three cannot be independently specified. Only two can be done as the third becomes dependent on the other two". I was wondering how the two capacitors and can independent and the third dependent?

Thanks!

\$\endgroup\$
2
  • \$\begingroup\$ Could you tell us what time he says that so we can get a better context? It is a 53 minute video after all. \$\endgroup\$
    – RICK
    Jun 29, 2014 at 23:45
  • \$\begingroup\$ It's around the 40 minute mark. When I get home from work, I can give you the exact time the professor talks about it. \$\endgroup\$
    – M S
    Jun 30, 2014 at 16:48

1 Answer 1

Reset to default
1
\$\begingroup\$

Three caps in series across a "10V" power supply. If one cap (C1) has 2V across it and another (C2) has 5 volts across it, the third HAS to have 3 volts across it because: -

2 + 5 + 3 =10

If the power supply was 0V it makes no difference: -

C1 has (say) 2V across it, C2 has 5V across it and the third must have -7V across it because

2 + 5 - 7 = 0

\$\endgroup\$
3
  • \$\begingroup\$ Looks suspiciously much like Kirchhoff's Voltage Law ;o) \$\endgroup\$
    – jippie
    Jun 29, 2014 at 20:23
  • \$\begingroup\$ @jippie describe first, let the dude take it on board then give it a name LOL \$\endgroup\$
    – Andy aka
    Jun 29, 2014 at 20:27
  • \$\begingroup\$ @Andyaka I think the author is referring to the capacitance of, not that voltage across each. That's how I remember it from school at any rate. \$\endgroup\$
    – RICK
    Jun 29, 2014 at 23:45

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.