Help me answer this question please Item 3 Electronic devices often use an RC ci

Question

Help me answer this question please Item 3 Electronic devices often use an RC circuit to protect against power outages as shown in the figure. Part A If the protector circuit is supposed to keep the supply voltage at least 75% of full voltage for as long as 0.19s, how big a resistance R is needed? The capacitor is 8.2MuF . Assume the attached electronics draws negligible current. Express your answer using two significant figures. R= kOhm Part B Between which two terminals should the device be connected, a and b, b and c, or a and c? The device should be connected between a and b terminals. The device should be connected between b and c terminals. The device should be connected between a and c terminals.

Explanation / Answer

The capacitor is uncharged until the switch is closed . The voltage across R will be maximum as V_C=0 V

So For part A Voltage across capacitor will be dependant on the time constant given by formula

voltage across the capacitor=fullvoltage*exp(-t/RC)

critical value of Volage(Vc) is 0.75V(full)

0.75V= V*exp(-t/RC)

-t/RC= ln(0.75)

t/RC=0.2877

t= 0.2877RC

R= 0.19/0.287*8.2*10-6 = 0.8Mohms

b) The capacitor is the mai compoent of the protector circuit ad should be connected between b and c

Related Questions

Navigate

• Browse (All)
• Browse H
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.