Wednesday

July 23, 2014

July 23, 2014

Posted by **linds** on Wednesday, March 21, 2012 at 1:51am.

(a) At what frequency is the current a maximum?

2.A series circuit contains only a resistor and an inductor. The voltage V of the generator is fixed. If R = 20 Ω and L = 2.8 mH, find the frequency at which the current is one-fifth its value at zero frequency?

- physics please help!! -
**drwls**, Wednesday, March 21, 2012 at 2:01am1) Maximum current occurs at resonant frequency

f = sqrt(LC)/(2 pi)

2) Compute the angular frequency w for which the impedance magnitude is increased by a factor of 5.

I = (1/5)(V/R) = V/|Z|

= V/sqrt[R^2 + (wL^2])

V cancels out; solve for w.

Then use

f = 2 pi w

- physics please help!! -
**linds**, Wednesday, March 21, 2012 at 2:05amCan you plug in the numbers for #1 please? I'm still a little confused.

- physics please help!! -
**drwls**, Wednesday, March 21, 2012 at 6:00amSorry about that. The LC term should have been in the denominator, for problem #1.

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