The figure below shows how a bleeder resistor is used to discharge a capacitor a

Question

The figure below 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. What is the time constant? ElectronicC circuit 185 ?F 240 k? Enviar RespuestaTries 0/5 How long will it take to reduce the voltage on the capacitor to 0.280% of its full value once discharge begins? Enviar RespuestaTries 0/5 If the capacitor is charged to a voltage VO through a 105-? resistance, calculate the time it takes to rise to 0.850Vo (This is about two time constants.)

Explanation / Answer

time constant T = RC = 240*10^3*85*10^-6 = 20.4 s

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the voltage across capacitor plates decreases as Vc = V*e^-(t/T)

for Vc = 0.28 V

0.28 V = V*e^-(t/20.4)

0.28 = e^-(t/20.4)

time taken = 26 s

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Time constant T = RC = 105*85*10^-6 = 0.008925 s

the voltage across capacitor plates increases as Vc = Vo*( 1 - e^-(t/T) )

for Vc = 0.85 Vo

0.85 Vo = Vo*( 1 - e^-(t/0.008925) )

0.85 = ( 1 - e^-(t/0.008925) )

time t = 0.01693 s <<<----------ANSWER

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