*62 Figure 27-64 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. There is a current through the lamp only when the potential difference across it reaches the breakdown volt- Figure 27-64 Problem 62. age V1; then the capacitor discharges completely through the lamp and the lamp flashes briefly. For a lamp with breakdown voltage VL = 72.0 V, wired to a 95.0 V ideal battery and a 0.150 µF capacitor, what resistance Ris needed for two flashes per second?

*62 Figure 27-64 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. There is a current through the lamp only when the potential difference across it reaches the breakdown volt- Figure 27-64 Problem 62. age V1; then the capacitor discharges completely through the lamp and the lamp flashes briefly. For a lamp with breakdown voltage VL = 72.0 V, wired to a 95.0 V ideal battery and a 0.150 µF capacitor, what resistance Ris needed for two flashes per second?

College Physics

1st Edition

ISBN:9781938168000

Author:Paul Peter Urone, Roger Hinrichs

Publisher:Paul Peter Urone, Roger Hinrichs

Chapter21: Circuits And Dc Instruments

Section: Chapter Questions

Problem 71PE: Figure 21.55 shows how a bleeder resistor is used to discharge a capacitor after an electronic...

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Figure 21.55 shows how a bleeder resistor is used to discharge a capacitor after an electronic device is shut off allowing a person to work on the electronics with less risk of shock, (a) What is the time constant? (b) How long will it take to reduce the voltage on the capacitor to 0.250% (5% of 5%) of its full value once discharge begins? (c) If the capacitor is charged to a voltage V0through a 100-O resistance, calculate the time it takes to rise to 0.865V0(This is about two time constants.)
Draw two graphs of charge versus time on a capacitor. Draw one for charging an initially uncharged capacitor in series with a resistor, as in the circuit in Figure 21.38, starting from t = 0. Draw the other for discharging a capacitor through a resistor, as in the circuit in Figure 21.39, starting at t = 0, with an initial charge Q0. Show at least two intervals of t.
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Regarding the units involved in the relationship t = RC, verify that the units of resistance times capacitance are time, that is, . F = S.
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