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Your latest invention is a car alarm that produces sound at a particularly annoy

ID: 2030026 • Letter: Y

Question

Your latest invention is a car alarm that produces sound at a particularly annoying frequency of 3545 Hz. To do this, the car-alarm circuitry must produce an alternating electric current of the same frequency. That's why your design includes an inductor and a capacitor in series. The maximum voltage across the capacitor is to be 12.0 V (the same voltage as the car battery). To produce a sufficiently loud sound, the capacitor must store 0.0156 J of energy. What values of capacitance and inductance should you choose for your car-alarm circuit?

C = µF L = µH

Explanation / Answer

Energy stored in capacitor is

U=(1/2)CV2

=>C =2U/V2=2*0.0156/122

C=216.67 uF

Resonant frequency

f=1/2pisqrt(LC)

=>L=1/4pi2f2C =1/4pi2*35452*(216.67*10-6)

L=9.303 uH