25-Solving Parallel RLC Step Response Problems

Online lecture for ENGR 2305, Linear Circuits, solving problems involving the step response of parallel RLC circuits. This is for a 16-week course taught to community college sophomores entering into an engineering program. The prerequisites for the course are second-semester calculus and differential equations.

[@wegdanfarea4697]

thanks for everthing

[@ontarget373]

Thanks

[@paulchu1051]

in the first exmaple, why the current of capitor(Ic 0+) is 24mA（@ video 4：52 ）? why it doesn't follow Current divider rule ？ thanks to answer！

[@EnjoyYourUniverse]

The C offers zero resistance at t=0. Given two paths, one with some resistance and one with zero, the current will choose the path with zero resistance. Of course this changes quickly after t=0. You could use current divider equation, compute i for R, but set resistance for C to zero, gives zero i for R.

[@stacarlsonlauspehus3161]

What if we need to determine the value of R is not given?

[@EnjoyYourUniverse]

I’m not sure, but I think I know what you’re asking. In that case, if you need to find R, then you would need to know which of the three cases you’re solving for, that is under, over, or critically damped. You would also need to know the alpha frequency or have enough information to figure it out.

[@stacarlsonlauspehus3161]

How to find the R value? Can you give me the formula?

[@stacarlsonlauspehus3161]

I have a similar question given but it states that we need to determine the R value to produce the three types of damping response and obtain the numerical expression of iL(t) at t>0 With values I=24mA, L=25mH, C=25nF, can you help me?

[@EnjoyYourUniverse]

@@stacarlsonlauspehus3161 Sounds like you want me to do your homework for you. Here’s what you need to do: Do the comparison between alpha and omega based on the case you want, then solve for R. After that follow the procedure in the video to in the currents and/or voltages.