AP Physics C Electricity : Understanding Capacitors
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Example Questions
Example Question #1 : Capacitors
A parallel plate capacitor has a capacitance of 
The relationship between capacitance, distance, and area is 
Now, we can use the values given in teh question to solve.
Example Question #1 : Capacitors
Charge is distributed uniformly over the area of the two plates of a parallel plate capacitor, resulting in a surface area charge density of 
Which of the following would not result in an increase in the measure of electric potential difference between the two plates?
Increase the value of the surface charge density, 
Increase the area, 
Increase the distance, 
Replace the material between the two plates with one of a lower dielectric constant,
Increase the area,
The electric potential difference created between the plates of a parallel plate capactor is given by the equation:
The charge can be calculated by using the equation:
The value of the capacitance is related to the dimensions of the capacitor with the equation:
Combining these equations yields:
The area becomes inconsequential, while the potential is directly proportional to the surface charge density and the distance between the plates, and inversely proportional to the dielectric of the material between the plates. Changing the area does not cause any change in the potential difference measured between the plates, and changing any of the other variables would cause a resultant change in the potential difference.
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