parallel-plate capacitor is made from two sheets of metal, each with an area of

Question

parallel-plate capacitor is made from two sheets of metal, each with an area of 2.0m2 separatedby asheet of plastic 1.5 mm thick The capacitance i The permittivity of air is = 8.854 × 10-12 F/m. The capacitance is C K . A / d. The voltage across the capacitor is V-E(1-e*Rc) and the current is 1= (ER)e"RC measured to be 0.15F switch R22.5 x 105 plastic Ca 0.15 -- a) What is the dielectric constant of the plastic? (5 pts.) The uncharged capacitor is connected in series with a resistor R-25 battery, and a switch, as shown above. The switch is then closed. current when the switch is closed? 10 6 , a 25 V What is the initial b) (5 pts.) (5 pts.) c) What is the voltage across the capacitor after t-7.5 s? 7.5 s? (5 pts.) d) What is the current in the circuit after

Explanation / Answer

a)We know that,

C = k e0 A/d

k = C d/ e0 A

k = 0.15 x 10^-6 x 1.5 x 10^-3/8.854 x 10^-12 x 2 = 12.71

Hence, k = 12.71

b)Just after the switch is closed:

I = V/R = 25/2.5 x 10^6 = 1 x 10^-5 A

Hence, I = 1 x 10^-5 A = 10 micro A

c)The voltage at any time t is given by:

V = V0 (1 - e^-t/RC)

V = 25 (1 - e^-7.5/2.5 x 10^6 x 0.15 x 10^-6) = 24.99 V

Hence, V = 24.99 V

d)current at any time is;

I = Vb/R e^-t/RC

I = 25/2.5 x 10^6 x e^-7.5/2.5 x 10^6 x 0.15 x 10^-6 = 2.06 x 10^-14 A

Hence, I = 2.06 x 10^-14 A

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

---

---

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