+ 14.28 points SerCP9 18.P034.WI. My Notes Ask Your Teacher Consider a series RC

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+ 14.28 points SerCP9 18.P034.WI. My Notes Ask Your Teacher Consider a series RC circuit for which R = 2.0 MQ, C = 6.0 F, and = 28 V. Find the charge on the capacitor 5 s after the switch is closed. Need Help?Watch itTalk to a Tutor + 14.28 points SerCP9 18.P035 My Notes Ask Your Teacher A charged capacitor is connected to a resistor and a switch as in the figure below. The circuit has a time constant of 1.60 s. Soon after the switch is closed, the charge on the capacitor is 70.0% of its initial charge. C (a) Find the time interval required for the capacitor to reach this charge. (b) If R = 200 k, what is the value of C? Need Help? Talk to a Tutor Telk le bter

Explanation / Answer

Problem 1

(a)Time constant RC = 2 Mega ohm into 6 micro Farad

Time constant = 12 seconds

As charging of capactor is governed by

q = qo (1 - exp(-t/RC)

As qo = CVo = 28 x 6 x 10-6

q = 1.68 x 10-4 (1- exp (-5/12))

q = 5.724 x 10-5 C

Is the required charge

Problem 2:

Discharging of capacitor through resistor is given by

q = qoexp(-t/RC)

given RC = 1.60 s

For, q = 0.70qo

0.70 = exp(-t/1.60)

t = -1.60 ln(0.70)

t = 0.57 seconds

Is the required answer

(b)

If R = 200 kilo Ohm

RC = 1.6 s

C = 1.6/200000 = 8 micro farad

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