A point charge q 1 = +2.40 ?C is held stationary at the origin. A second point c

Question

A point charge q1 = +2.40 ?C is held stationary at the origin. A second point charge

q2 = -4.30 ?C moves from point a (x = 0.150 m, y =0) to point b (x = 0.250 m, y = 0.250 m).

1. What is the electric potential energy of the system when q1 is at the origin and q2 is in the original position?

2. What is the electric potential energy of the system when q1 is at the origin and q2 is in the final position?

3. How much work is done by the electric force on q2 to move it from the original position to the final position?

Explanation / Answer

A point charge with a charge q1 = 2.60uC is held stationary at the origin.

A second point charge with a charge q2= -4.10uC moves from the point x=0.170 m, y=0 to the point x=0.270m , y=0.290m .

Initial seperation = r1 =0.170 m

Final seperation = r2 = sq rt [0.27^2+0.29^2]=sq rt [0.0729+0.0841]= sq rt =0.157=0.396 m

r1 - r2 =0.170 - 0.396 = - 0.226 m

r1r2=0.06732 m^2

Work is done by the electric force on q2= W =change in potential energy

W =kq1q2 [1/r2 - 1/r1]

W = 9*10^9*2.6*10^-6*(-4.1)*10^-6* [ -0.226 ] / 0.06732

W = 21.68244*10^-3/0.06732

W = 3.22080*10^-1 J

3.22080*10^-1 J work is done by the electric force on q2

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