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For more information, please see full course syllabus of AP Physics C/Electricity and Magnetism

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### Electric Potential, Part 2

• The electric potential produced by a point charge Q at a point a distance r away is kQ/r.
• For a collection of point charges Q1, Q2, Q3, …, the electrostatic potential energy is equal to U = (1/2)*Sum (i, j) k*Qi*Qj / r_ij, where r_ij is the distance between charges Qi and Qj. The factor of 1/2 is inserted in order to avoid double counting. In other words, we sum over the pairs of charges.
• The electric field vector may be obtained from the electric potential: E = -grad V; i.e., E is the negative of the gradient of V.

### Electric Potential, Part 2

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

• Intro 0:00
• Potential of a Point Charge 0:32
• Potential Difference Between A to B
• Draw a Circle
• Tangential to Sphere
• Moving Normally From Sphere
• Potential Energy of a Collection of Charges 26:33
• Potential Energy of Two Charges
• Work Done in Assembling the Configuration
• Bringing From Infinity to New Location
• Work Done by External Agent
• Potential Energy of the System
• Potential Energy for Two Charges
• Example 44:49
• Two Charges
• Speed at Infinity
• Electric Field from the Potential 51:12
• Finding E if V is Given
• Electric Dipole 56:22
• Two Equal and Opposite Charges Separated By a Distance
• If a << r1 or r2
• Example 1: Two Point Charges
• Example 2: Two Insulating Spheres
• Example 3: Electric Potential of Space