AP Physics C Electricity : Understanding Electrostatics
Study concepts, example questions & explanations for AP Physics C Electricity
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Example Questions
Example Question #1 : Electricity
A hollow metal sphere with a diameter of 10cm has a net charge of 
Relevant equations:
Anywhere outside the metal sphere, the electric field is the same as it would be for a point charge of the same magnitude, located at the center of the sphere. So, calculate the electric field of a point charge given:
Plugging in gives:
Example Question #2 : Electricity
Two infinite parallel conducting sheets each have positive charge density 
Relevant equations:
Electric field is additive; in other words, the total electric field from the two planes is the sum of their individual fields:
The direction of the electric field is away from positive source charges. Thus, to the right of these positively charged planes, the field points away to the right.
Example Question #3 : Electricity
Consider a spherical capacitor made of two nested spheres. The smaller sphere has a radius of 
Which of the following equations accurately describes the capacitance of this spherical capacitor?
Due to symmetry, this scenario would not produce capacitance
To solve this problem, we will need to derive an equation.
We know that:
We can use Gauss's law to derive the electric field between the two circles yielding:
Doing our integration with respect to 
We can plug this back into our equation for capacitance to get:
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All AP Physics C Electricity Resources
