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## Homework Statement

http://i.imgur.com/FxuxHjW.png?1

L = 1.6 mH, C = 100 μF. Determine the frequency at which the total current will be 0. (The picture shows 3L, which is 3*L, so 3*1.6 mH.) There's also a hint "Use the vector diagram." The result is 2.5 kHz which I cannot get.

2. Homework Equations

2. Homework Equations

[tex]f=\frac{1}{2\pi\sqrt{L\cdot C}}[/tex]

## The Attempt at a Solution

I tried simply plugging the numbers in the formula but it doesn't work. :) I think I don't understand what's going on to actually solve the problem. I think what happens in one parallel is: current will be 0 because the values of capacitance and inductance are of the same size but of opposite signs, so there are going to be two currents which cancel out; some books say there's also infinite resistance (by the formula R_parallel = R_1*R_2/(R_1 + R_2), so I'm guessing, since X_C = - X_L, when you add them, the denominator is 0 which implies infinite resistance)...

I've never seen such a problem... Also, I'm not sure how to solve this using a phasor diagram as I cannot actually represent L, C, or reactances themselves... (only voltages and currents).

Thanks in advance.