A piezo sounder is driven by letting a series loop ring down

PHYSICS · Multi-part · Fermi University Physics · Electricity, Magnetism & Electromagnetism · Electric current and circuits · Electromagnetic induction and alternating-current circuits

Electricity, Magnetism and Electromagnetism, Ch Transients: RC, RL and LC circuits

Problem

A piezo sounder is driven by letting a series loop ring down. The loop is a coil of self-inductance

L = 4.7\,\mathrm{mH}

, a capacitor

C = 47\,\mathrm{nF}

and a total resistance

R = 220\,\Omega

(the coil's winding resistance is already included in

R

). At

t = 0

the capacitor is charged and the loop is closed; no source acts on it afterwards, and the components are otherwise ideal. ((a)) Work out the critical resistance

2\sqrt{L/C}

for this loop and state whether the charge rings or dies away without swinging. ((b)) If it rings, calculate the ringing frequency

f_{\mathrm{d}} = \omega_{\mathrm{d}}/2\pi

in kilohertz.

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