Differential Equation from RLC Circuit

• Nov 13th 2011, 09:21 PM
p75213
Differential Equation from RLC Circuit
Can somebody show the missing step/s between (8.18) and (8.19)? The equation comes from a book on electrical circuits.
• Nov 13th 2011, 09:22 PM
Prove It
Re: Differential Equation from RLC Circuit
Quote:

Originally Posted by p75213
Can somebody show the missing step/s between (8.18) and (8.19)? The equation comes from a book on electrical circuits.

Try working in reverse, it's just a recognition of evaluating a derivative using a product rule...
• Nov 13th 2011, 10:14 PM
p75213
Re: Differential Equation from RLC Circuit
Quote:

Originally Posted by Prove It
Try working in reverse, it's just a recognition of evaluating a derivative using a product rule...

I see what you mean.
• Nov 15th 2011, 05:18 AM
rulmismo
Re: Differential Equation from RLC Circuit
Just to confirm, being i the imaginary unit, first term should vanish as di/dt=0?
• Nov 15th 2011, 06:18 AM
Ackbeet
Re: Differential Equation from RLC Circuit
Quote:

Originally Posted by rulmismo
Just to confirm, being i the imaginary unit, first term should vanish as di/dt=0?

Most definitely NOT. In electrical engineering, i is current, and j is the square root of minus one, in order to avoid just this confusion. The current i = i(t) is a function of time.