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Lecture Comments (3)

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Post by Kevin Moe on February 9 at 01:49:31 PM

On the equation for equilibrium of net force on each sphere, q^2 = 4L^2(mg)tan(theta)sin^2(theta), where did the constant "k" go?

1 answer

Last reply by: bakar yasin
Tue Dec 11, 2012 9:38 PM

Post by Jeremy Zhang on March 18, 2012

isnt Tan of something opposite over adjacent? So isnt it mg/(F) not F/mg?

Coulomb's Law

  • Coulomb’s law: if two charges q1 and q2 are separated by a distance r, the magnitude of the force between them is F = k |q1| |q2| / r^2; the force is repulsive if both charges are negative or both are positive, and is attractive otherwise.
  • If the force is in Newtons, q1 and q2 in Coulombs, and r in meters, then the constant k that appears in Coulomb’s law is equal to 9 x 10^9 SI units.

Coulomb's Law

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
  • Coulomb's Law 0:59
    • Two Point Charges by Distance R
    • Permitivity of Free Space
  • Charges on the Vertices of a Triangle 8:00
    • 3 Charges on Vertices of Right Triangle
    • Charge of 4, -5 and -2 micro-Coulombs
    • Force Acting on Each Charge
  • Charges on a Line 21:29
    • 2 Charges on X-Axis
    • Where Should Q should be Placed, Net Force =0
  • Two Small Spheres Attached to String 31:08
    • Adding Some Charge
    • Equilibrium Net Force on Each Sphere = 0
  • Simple Harmonic Motion of Point Charge 37:40
    • Two Charges on Y-Axis
    • Charge is Attracted
    • Magnitude of Net Force on Q
  • Extra Example 1: Vertices of Triangle
  • Extra Example 2: Tension in String
  • Extra Example 3: Two Conducting Spheres
  • Extra Example 4: Force on Charge