Which of the following materials has the highest dielectric constant?
a. air
b. Mylar
c. paper
d. Pyrex glass
e. water
[Ques. 2] Two spheres are made of conducting material. Sphere 2 has twice the radius of Sphere 1 . What is the ratio of the capacitance of Sphere 2 to the capacitance of sphere 1?
a. 1, since all conducting spheres have the same capacitance.
b. 2
c. 4
d. 8
e. A single sphere has no capacitance since a second concentric spherical shell is necessary to make a spherical capacitor. Thus, none of the answers above is correct.
[Ques. 3] Which of the following statements is incorrect?
a. Capacitance is always positive.
b. The symbol for potential difference between the plates of a capacitor is .
c. Water is a polar molecule.
d. When a dielectric is placed in a capacitor it serves to reduce the electric field.
e. Nonpolar molecules cannot be used for dielectric material in a capacitor.
[Ques. 4] A parallel plate capacitor is connected to a battery and charged to voltage V. Leah says that the charge on the plates will decrease if the distance between the plates is increased while they are still connected to the battery. Gertie says that the charge will remain the same. Which one, if either, is correct, and why?
a. Gertie, because the maximum voltage is determined by the battery.
b. Gertie, because the capacitance of the capacitor does not change.
c. Leah, because the capacitance decreases when the plate separation is increased.
d. Leah, because the capacitance increases when the plate separation is increased.
e. Neither, because the charge increases when the plate separation is increased.
[Ques. 5] A parallel plate capacitor is charged to voltage V and then disconnected from the battery. Leopold says that the voltage will decrease if the plates are pulled apart. Gerhardt says that the voltage will remain the same. Which one, if either, is correct, and why?
a. Gerhardt, because the maximum voltage is determined by the battery.
b. Gerhardt, because the charge per unit area on the plates does not change.
c. Leopold, because charge is transferred from one plate to the other when the plates are separated.
d. Leopold, because the force each plate exerts on the other decreases when the plates are pulled apart.
e. Neither, because the voltage increases when the plates are pulled apart.
[Ques. 6] A 0.16 pF parallel-plate capacitor is charged to 10 V. Then the battery is disconnected from the capacitor. When 1.00 107 positive charges of magnitude e are now placed on the positive plate of the capacitor, the voltage between the plates changes by
a. 5.0 V.
b. 1.1 V.
c. 0 V.
d. +1.1 V.
e. +5.0 V.
[Ques. 7] A 0.16 pF parallel-plate capacitor is charged to 10 V. Then the battery is disconnected from the capacitor. When 1.00 107 electrons are now placed on the negative plate of the capacitor, the voltage between the plates changes by
a. 5.0 V.
b. 1.1 V.
c. 0 V.
d. +1.1 V.
e. +5.0 V.
[Ques. 8] A 0.120 pF parallel-plate capacitor is charged to a potential difference of 10.0 V and then disconnected from the battery. A cosmic ray burst creates 1.00 106 electrons and 1.00 106 positive charges between the plates. If the charges do not recombine, but reach the oppositely charged plates, by how much is the potential difference between the capacitor plates reduced?
a. 1.33 V
b. 7.34 V
c. 8.67 V
d. 1,330 V
e. 8,670 V
[Ques. 9] An initially uncharged parallel plate capacitor of capacitance C is charged to potential V by a battery. The battery is then disconnected. Which statement is correct?
a. There is no charge on either plate of the capacitor.
b. The capacitor can be discharged by grounding any one of its two plates.
c. Charge is distributed evenly over both the inner and outer surfaces of the plates.
d. The magnitude of the electric field outside the space between the plates is approximately zero.
e. The capacitance increases when the distance between the plates increases.
[Ques. 10] A 30-F capacitor is charged to an unknown potential V0 and then connected across an initially uncharged 10-F capacitor. If the final potential difference across the 10-F capacitor is 20 V, determine V0.
a. 13 V
b. 27 V
c. 20 V
d. 29 V
e. 60 V
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