The figure shows the circuit of a flashing lamp, like those attached to barrels

Question

The figure shows the circuit of a flashing lamp, like those attached to barrels at highway construction sites. the fluorescent lamp L (of negligible capacitance) is connected in parallel across the capacitor C of an RC circuit. the re is a current through the lamp only when the potential difference across it reaches the breakdown voltage VL; the n the capacitor discharges completely through the lamp and the lamp flashes briefly. For a lamp with breakdown voltage VL = 68. 1 V, wired to a 98. 1 V ideal battery and a 0. 152 mF capacitor, what resistance R is needed for 3 flashes per second?

Explanation / Answer

V =VL[1-e^(-t/RC)]

68.1 =98.1[1-e^(-0.2/R*0.152*10^-3)]

0.3058 =e^(-1315.8/R)

R=1110.5 ohms or 1.11kohms

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