Sinusoidal steady-State proplem

[tinhnho]

Hi everyone

I have a hard time to figure out these proplems in the picture.

Here are my solutions:

1) V1 = V*R/(R+ L) (voltage divider)
but we have V = cos(wt)
=> V1 = cos(wt)*R/(R+L)

2) L* di/dt + R*I = V1*cos( w*t + **broken link removed** )
==> V1 = (L*di/dt + R*I)/cos(w*t +**broken link removed**)

3) ?

4) V2 = R/(R +C)

5)?

6)?

7) ?

thanks for looking

 

[Roff]

Two hints:

1. Inductive reactance=jwL
2. Capacitive reactance=1/jwC

You are using L and C for the respective reactances. This is incorrect.

 

[tinhnho]

Hi there

thanks for respond. Because the question is aksing for the formula won't contain j (if you are talking about question #1). I dont remember the formula for find the radian frequency w ( in question #3 and #6), please anyone help me ?

thanks for reading

p/s: there is a requirement for the question $1 at the end of the picture, thanks

 

[Styx]

It is a voltage divider:

V1 = V* R/(R+jwL)

and also if you remeber your complex arithmatics you should be able to find the magnitude (and equally the phase) for this equation

|V1| = SQRT( Re(V1)^2 + Im(V1)^2 )


plus this looks like homework and have given too much help.

 

[tinhnho]

thanks
i think i need to rewiew complex number.
BTW, last question, anyone know how to find w ? thanks

 

[Roff]

w=2*pi*f. Have you been sleeping during class?

 

[tinhnho]

yes, i know that formula, the reason i asking because i dont know how to find f, i know it is not that hard, it just because i wasn't pay attention, what a shame...

p/s: given R and L value, and phasor value = 45 degree. They are asking for w

 

[Optikon]

yes, i know that formula, the reason i asking because i dont know how to find f, i know it is not that hard, it just because i wasn't pay attention, what a shame...

Well, at least he admits it.

Since, you've gone through all the trouble scanning the pages etc etc.. just take an hour and review the material in the text. Sleep with the book under your pillow.