Question

1. A 26.0-Ω resistor, a 12.0-µF capacitor, and a 17.0-mH inductor are connected in series with a 150-V generator.
(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?

Answer 1

1) 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

Answer 2

Can you plug in the numbers for #1 please? I'm still a little confused.

Answer 3

Sorry about that. The LC term should have been in the denominator, for problem #1.