Page |2 TU Department of Physics, Astronomy, &Geosciences; Test 2 6. A 50 uF air

Question

Page |2 TU Department of Physics, Astronomy, &Geosciences; Test 2 6. A 50 uF air-filled capacitor is immersed in silicone oil, which has a dielectric constant of 2.6. The capacitor is connec o a 24 V battery, What is the energy stored in the capacitor with the oil added between the plates? A) 1560 B)3120 c37440 J D) 74880 u A 150?F capacitor is connected in series with a 50 kanesstor. The capacitor/resistor is placed in a 7, charging circuit and the capacitor is char capacitor plates after 15 seconds? ged by a 10.0 volt power supply. How much voltage is on the A) 1.4 V B) 3.7 V C) 5.0 v D) 8.6 V E) 10.0 V 12 V what is the potential difference unknown circuit element? Does the potential increase or decrease when traversing through this element in the direction assigned to I? 8. across the A. ?? decreases by 2 Vin the direction of L B. AV increases by 2 V in the direction of I. C. ?? decreases by 10 V in the direction of 1. D. AV increases by 10 V in the direction of I. 9. A 100 pF parallel plate capacitor has a voltage of 120 volts across the plates; the battery is removed and the space between the plates is filled with mica (k-5.4). What is the voltage across the plates after adding the dialectric? A) 80 V B)432 V C) 648 V D) 22V. 10. Two space heaters are operated at 120 V. Heater I has twice the resistance of heater 2. Which heater produces more heat? A) heater 1B) heater 2Both the same

Explanation / Answer

6)Ans is

(C)37440 uJ

explanation

C' = k C

C' = 2.6 x 50 uF = 130 uF

We know that, U = 1/2 C V^2

U = 0.5 x 130 x 10^-6 x 24^2 = 37440 x 10^-6 J

Hence, U = 37440 uJ

7)Ans is:

D)8.6 V

explanation

Vc = Vm(1 - e^-t/RC)

Vc = 10 (1 - e^-15/50 x 10^3 x 150 x 10^-6) = 8.6 V

Hence, Vc = 8.6 V

8)(A)

because:

Vu = 12 - (6 + 8) = -2 V

9)(D)22 V

Q = CV = 100 x 120 = 12000 pF

C' = 5.4 x 100 = 540 pF

charge is conserved

V = Q/C' = 12000/540 = 22 V

Hence, V = 22 V

10)Heater 1

P = I^2 R = V^2/R

inversely propotional to R

more resistance less heat

(A)Heater1

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