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GR0877 Problem 36

PROBLEM STATEMENT: This problem is still being typed.

SOLUTION: (A) The magnetic energy is LI^2/2. In LC-contour with initial conditions q(t = 0) = q_0 and I_0 \equiv (dq/dt)_0 = 0 the charge on the capacitor is a cosine function of time and the current is, therefore, a sine function. Thus, magnetic energy is a square of the sine function of time with some proportionality factor. That is, it passes through the origin and has a form similar to (A).

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Categories: 0877 Tags: , , , ,
  1. Arturodonjuan
    28.08.2016 at 10:12

    Quick solution:

    Ideal LC-circuits will always be sinusoidal, so answer choices (C), (D), and (E) are immediately out. Then, remember that magnetic energy in an inductor is stored in the magnetic field which it generates, which depends on the amount of current running through the inductor. However, the inductor chokes all current right at the beginning (i.e. when the switch is closed), so (A) must be the answer.

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