16.4 Dielectrics 74. MC Putting a dielectric in a charged parallel-plate capacit

Question

16.4 Dielectrics

74.     MC Putting a dielectric in a charged parallel-plate capacitor that is not connected to a battery (a) decreases the capacitance, (b) decreases the voltage, (c) increases the charge, (d) causes a discharge because the dielectric is a conductor.  

75.     MC A parallel-plate capacitor is connected to a battery. If a dielectric is inserted between the plates, (a) the capacitance decreases, (b) the voltage increases, (c) the voltage decreases, (d) the charge increases.  

76.     MC A parallel-plate capacitor is connected to a battery and then disconnected. If a dielectric is then inserted between the plates, what happens to the charge on its plates: (a) The charge decreases, (b) the charge increases, or (c) the charge stays the same?  

80.     l A capacitor has a capacitance of 50 pF, which increases to 150 pF when a dielectric material is between its plates. What is the dielectric constant of the material?  

81.      l A 50-pF capacitor is immersed in silicone oil When the capacitor is connected to a 24-V battery, what will be the charge on the capacitor and the amount of stored energy?  

82.      ll The dielectric of a parallel-plate capacitor is to be constructed from glass that completely fills the volume between the plates. The area of each plate is (a) What thickness should the glass have if the capacitance is to be (b) What is the charge on the capacitor if it is connected to a 12-V battery?  

16.5 Capacitors in Series and in Parallel

85.     MC Capacitors in series have the same (a) voltage, (b) charge, (c) energy storage.  

86.      MC Capacitors in parallel have the same (a) voltage, (b) charge, (c) energy storage.  

87.      MC Capacitors 1, 2, and 3 have the same capacitance value C. 1 and 2 are in series and their combination is in parallel with 3. What is their effective total capacitance. (a) C, (b) 1.5C, (c) 3C, or (d)   

92.     l What is the equivalent capacitance of two capacitors with capacitances of and when they are connected (a) in series and (b) in parallel?

Explanation / Answer

74. (b) decreases the voltage

75. (d) the charge increases

76. (c) the charge stays the same

80. K=150/50 = 3

81. Q=CV= 50*24 = 1200 pC = 1.2 nC

U= 0.5CV^2= 0.5*50E-12*24*24 = 1.44E-8 J

82. incomplete Question

85. (b) charge

86. (a) voltage

87. (b) 1.5C

92. Series:: Ceq = C1*C2/(C1+C2)

Parallel :: Ceq = C1+C2

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