Practice_Test_3_with_Solutions

# Practice_Test_3_with_Solutions - Solutions to Practice Test...

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Solutions to Practice Test 3 1. Two metal plates separated by a distance of 0.5 mm are charged oppositely and each carry a charge density 600 µ C/m 2 . If ε o = 8.85 x 10 -12 , what is the electric field in between the plates? Electric field between two oppositely charged parallel plates is: 62 7- 1 -12 600 10 Cm 6.78 10 67.8 MVm 8.85 10 o E σ ε × == = × = × a. 67.8 MVm -1 2. What is the potential difference between the two plates in question 1? V = E dx = 6.78 × 10 7 V m -1 × 0.0005 m = 3.4 × 10 4 V = 34 kV c. 34 kV 3. If E is the electric field between two metal plates separated by a distance d, the potential difference between the plates is c. Ed 4. A conductor carries a charge Q coulombs and its potential is V volts. The capacitance of the conductor is: b. Q/V F 5. If now more charges are added to the conductor in question 4, Capacitance of a conductor depends only on its physics dimensions. c. its capacitance will remain the same 6. The capacitance of a capacitor depends on a. the area of the capacitor plates 7. When 3.0 µ C charge is given to a capacitor, the potential difference between the plates is 2.0 V. What is the capacitance of this capacitor? 6 6 31 0 C 1.5 10 1.5 F 2.0 V Q CF V µ × = × = c. 1.5 µ F 8. If the distance between the plates of a parallel plate capacitor is doubled, The capacitance of a parallel plate capacitor is inversely proportional to the distance between the plates. If the distance is doubled, the capacitance will be halved. d. the capacitance becomes half its original value. 9. A 100 µ F capacitor is charged by connecting it across a 100 V battery. The charge on the capacitor plate is

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-6 2 100 10 F 100 V 10 0.01 C QC V C == × × = = b. 0.01 C 10. If a dielectric is introduced between the plates of a parallel plate capacitor. Which of the following statements is not true? The bound charges on the dielectric will set up an electric field opposite to the original field causing a decrease in the net electric field and causing a decrease in the potential difference between the plates. d. The potential difference between the plates increases 11. A parallel plate air capacitor has plates of area 0.2 m 2 which are separated by 2 mm. The capacitance of this capacitor is For air, dielectric constant κ = 1. The capacitance of a parallel plate capacitor is: 12 10 0 3 1 8.85 10 0.2 8.85 10 0.9 nF 21 0 A C d κε ×× × = × × c. 0.9 nF 12. If a dielectric material of dielectric constant k = 3.5 is introduced between the two plates, the capacitance will be: 12 9 0 3 3.5 8.85 10 0.2 3.0 10 3.1 nF 0 A C d × = × = × c. 3.1 nF 13. If you charge the capacitor in question 12 by connecting it across a 100-V battery, what is the energy stored in the capacitor? Energy of a charged capacitor is: 29 2 5 11 3 10 100 1.5 10 15 22 E CV J µ −− × × × = × = a. 15 µ J 14.
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Practice_Test_3_with_Solutions - Solutions to Practice Test...

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