1.
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Four simulations represent parallel plate capacitors. Which of the four capacitors would you expect the effect of fringing to be minimal, i.e. the capacitance is C=e0A/d? You can click-drag and observe the electric potential at that point. Note: There is a 1-5% intrinsic error in the calculation of charge.
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| All of the capacitors. |
| Capacitor 4 only. |
| Capacitors 3 and 4. |
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2.
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A capacitor depicted above is made of two charged plates each of surface area A=20cm2 (the plates are maintained at a constant voltage, the charge is given in fC (femtoCoulombs, 10-15 C), and distance is given in centimeters). Drag the blue capacitor plate into place 0.5 cm from the red plate. What happens to the total charge on the plates, and where does this charge come from? You can click-drag and observer the electric field at that point. Note: There is a 1-5% intrinsic error in the calculation of charge. Start
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| Increases. The charge comes from moving the plates together. |
| Decreases. |
| Increases. The charge comes from the battery that maintains the potential difference. |
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3.
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Calculate the capacitance of the system of two charged plates of surface area A=20cm2 when the separation between these plates is 0.5 cm (the plates are maintained at a constant voltage, the charge is given in fC (femtoCoulombs, 10-15 C), and distance is given in centimeters). You may drag the blue capacitor plate into place. You can click-drag and observe the electric field at that point. The light red and light blue circles represent the position of the charge on the capacitor plates. Note: there is a 1-5% intrinsic error in the calculation of charge. Start
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| Cannot determine, do not know potential difference. |
| 22.1 pF. |
| 0.354 nF. |
| 3.54 pF. |
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4.
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A capacitor is made out of two concentric radially symmetric conducting objects as shown in the animation. However, from your point of view (a 2-d slice) you cannot tell whether they have a spherical or cylindrical geometry. Determine the geometry of the shells. You can click-drag and observer the electric field and the electric potential at that point. Start
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| Cylindrical. |
| Spherical. |
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5.
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A capacitor is made out of a sphere and a spherical shell maintained at a constant potential difference as shown in the animation (charges are given in mC and distances are given in centimeters). You may click-drag on the inner sphere to resize it. What happens to the capacitance of the system when the inner sphere is resized? Note: there is a 1-5% intrinsic error in the calculation of charge. Start
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| The capacitance stays the same. |
| The capacitance increases/decreases as the inner sphere increases/decreases in radius. |
| The capacitance increases/decreases as the inner sphere decreases/increases in radius. |
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6.
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The capacitance of a parallel plate capacitor can be altered by dragging (drag from the middle) a conducting block in between the two plates (charge given in mC and position given in centimeters). The light red and light blue circles represent the position of the charge on the conductor. What is the ratio of the new capacitance to the old capacitance? Note: There is a 1-5% intrinsic error in the calculation of charge. Start
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| 1 |
| 0.6 |
| 1.7 |
| 2 |
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7.
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The capacitance of a parallel plate capacitor can be altered by dragging (drag from the middle) the conducting block centered in between the two plates, to either the far right or the far left position (charge given in mC and position given in centimeters). The light red and light blue circles represent the position of the charge on the conductor. What is the ratio of the maximum capacitance to the minimum capacitance? Note: There is a 1-5% intrinsic error in the calculation of charge. Start
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| 1 |
| 0.6 |
| 1.7 |
| 2 |
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8.
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Two conducting plates are placed one above the other and connected to a battery as shown in the animation (charge given in mC and position given in centimeters). The bottom plate can be moved by click-dragging near the center of the plate. You can measure the voltage and the electric field at any point by click-dragging. Note: There is a 1-5% intrinsic error in the calculation of charge. Which of the following statements is true? Start
Interactive Hint More Help: Show electric field.
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| The energy required to move an electron from the red plate to the blue plate does not depend on the position of the blue plate. |
| The electric field between the blue and red plates is independent of the position of the blue plate. |
| The blue and red plates form a capacitor. Their capacitance is independent of the position of the blue plate. |
| The energy stored between the two plates is independent of the position of the blue plate. |
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9.
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The two rectangles have uniform positive and negative charge densities (charge given in mC and position given in centimeters). Drag the bottom plate and observe the change in the potential energies of the plates. Why does the potential energy decrease when the plate separation decreases? You can measure the voltage at any point by click-dragging. Note: There is a 1-5% intrinsic error in the calculation of charge. Start
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| The capacitance of the system decreases. |
| The potential difference between the plates decreases. |
| Positive work needs to be done on the system to create the charge separation and this energy is recovered by moving the plates closer together. |
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10.
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The capacitor plates depicted above are maintained at a constant charge (charge given in mC and position given in centimeters). What is the capacitance of the system when the plates are 0.5 cm apart? Note: There is a 1-5% intrinsic error in the calculation of charge. Start
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| 0.45 pF. |
| 0.45 mF. |
| Cannot determine, do not know the voltage. |
| 0.25 pF. |
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11.
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Click-drag the dielectric block into the capacitor (charge given in >mC and position given in centimeters). Observe how the electric field and the charge on the capacitor and the dielectric change when you move the dielectric. The light red and light blue circles represent the position of the charge on the dielectric. What is the dielectric constant of the slab? You can measure the voltage and the electric field at any point by click-dragging. Note: There is a 1-5% intrinsic error in the calculation of charge. Start
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| 3.2 |
| 0.4 |
| 2.1 |
| 2.4 |
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12.
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Click-drag the dielectric spherical shell into the spherical capacitor (charge given in mC and position given in centimeters). Observe how the electric field and the charge on the capacitor and the dielectric change when you move the dielectric. What is the dielectric constant of the dielectric shell? You can measure the voltage at any point by click-dragging. Note: There is a 1-5% intrinsic error in the calculation of charge. Start
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| 2.2 |
| 1.9 |
| 2.5 |
| 0.4 |
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13.
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Click-drag the dielectric block into the capacitor (charge given in mC and position given in centimeters). Observe how the electric field and the charge on the capacitor and the dielectric change when you move the dielectric. What is the ratio of the new capacitance to the old capacitance? You can measure the voltage and the electric field at any point by click-dragging. Note: There is a 1-5% intrinsic error in the calculation of charge. Start
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| 1.1 |
| 1.5 |
| 0.9 |
| 4 |
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14.
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Click-drag the dielectric blocks, dielectric constants k1= 2.4 and k2 respectively, into the capacitor (charge given in mC and position given in centimeters). Observe how the electric field and the charge on the capacitor and the dielectric change when you move the dielectric. What is k2? You can measure the voltage and the electric field at any point by click-dragging. Note: There is a 1-5% intrinsic error in the calculation of charge. Start
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| 1.8 |
| 0.7 |
| 1.3 |
| 0.5 |
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15.
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Click-drag the dielectric blocks, dielectric constants k1= 4 and k2 respectively, into the capacitor (charge given in mC and position given in centimeters). What is k2? You can measure the electric field at any point by click-dragging. Note: There is a 1-5% intrinsic error in the calculation of charge. Start
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| 3.1 |
| 1.1 |
| 2.5 |
| 0.5 |
