Recent content by just.karl

help? please?

Work Done by Air "pressure difference" Homework Statement Air that initially occupies .14 m^3 at a gauge pressure of 103.0kPa is expanded isothermally to a pressure to 101.3 kPa and then cooled at constant pressure until it reaches its initial volume. Compute the work done by the air. (Gauge...

so then it would be 1/do + 1/2do = 1/40?

I understand that you use both equations, but the part I'm getting hung up on is how you solve for d_o with 1/do + 1/di = 1/F from my understanding it goes to -2/do + 1/do = 1/40 and the answer from that comes out to be -40 =do I then put that into the mdo=di equation and get 80. I'm...

So m d_o = -d_i (-2)(-40)= -d_i so then it comes out to be -80cm but in the back of the book it says it's 1.2m.

it should be -2?

If you want to produce an image of a bulb that is enlarged by a factor of 2, how far from the wall should the lens be placed. Focal length is 40cm. I know you use 1/d_o + 1/d_i =1/f and m= -d_i/d_o but how do you find d_o? -2/d_o +1/d_o =1/f ? but it comes out to 40cm and not 60cm...

(a)Find the frequency at which a 33 uF capacitor has the same reactance as a 33 mH inductor. (b) What is the resonance frequency of an LC circuit made with this inductor and capacitor. Well I believe the equation I use is 1 / (2 Pie \sqrt{}LC) but when I use it I come out with a answer very...

Ah, I found what I did. I forgot to square (1/wC), it comes out with the right answer now. Thanks for your help! I really appreciate it.

Alright.., when I plug in the numbers it comes out to be .9987 and the answer in the back of the book says .967. So that is probably just rounding error on my part I'm guessing?

If I use cos(theta) = R / Z then I don't use the voltage at all to solve for it?

I understand that, so then it would be P/IV=cos0 but what I don't understand is how you relate the capacitor and frequency into it. Since I can solve for "I" and "P" by P=V^2/R and then find "I" by P=IR.

Find the power factor for an RC circuit connected to a 70Hz generator with an rms voltage of 125V. The values of R and C in this circuit are 105ohms and 82.4microfarads, respectively. The equation I think you use is P=IVcos\oslash and also z= square root of R^2+(1/wc)^2 and cos0 = R/Z...

The forum is usually pretty helpful, but you should include a attempt at your solution and relevant equations also. You'll be more likely to get a response.

Sorry for the long delay on the reply. I forgot about it and my exam is tomorrow. So I want to figure this out. So V=Ed and C=e_oA/d so then Q=Ee_oA and A=\Phi/E ? Am I on the right track at all?