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### Electric Fields, Potential, and Capacitors Sample Problems

- A +40 mC test charge is placed in an electric field produced by a +5 C charge. It experiences a 6 N force. What is the strength of the electric field at this point?
- A +3 mC test charge is placed in a 20,000 N/C field. What force does it experience?
- A test charge experiences an electric field of 400,000 N/C at a point 1 cm away. What is the magnitude of the charge producing the field?
- 30 J of work is done to move a +5 C charge from one point to another in an electric field. What is the difference in potential between the two points?
- How much work is done to move an electron across a potential of 3 V?
- Two parallel plates are separated by 0.5 m. An electric field of 6000 N/C exists between the plates. What is the potential difference between the plates?
- A potential difference of 60 V exists between two parallel plates separated by 3 cm. What electric field exists between the plates?
- An oil drop carrying a charge of -8 x 10
^{-19} C is suspended between two plates separated by 8 mm. A 1200 V potential difference exists between the plates. What is the weight of the suspended drop?
- An oil drop weighs 5.8 x 10
^{-14} N. It is suspended in a 3000 N/C field. What is the charge of the drop? How many electrons does it carry?
- What is the capacitance of a capacitor carrying a charge of 0.00012 C and having a 6 V potential difference?
- What charge exists on a 30 mF capacitor with a 120 V potential difference between its plates?
- Lab-type problem: A 330 mF capacitor and a 100
W resistor are used. The signal generator is set for 4 V.
- beginning time: 1.2471 sec
- time to reach 2 V: 1.2671 sec
- maximum voltage: 3.95 V
- area under curve: 0.0015303 A sec
- Calculate the theoretical value for the charging half-life.
- Calculate the experimental value for the half-life.
- Calculate an experimental value for the capacitance using your charging half-life.
- Use the area under the curve and the maximum voltage to calculate the energy stored.
- Use the maximum voltage and your experimental value for the capacitance to calculate the energy stored.

Electric Fields, Potential, and Capacitors
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Electric Fields, Potential, and Capacitors
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