d) determine the x-coordinate of the point on the line between the two charges a
ID: 2295657 • Letter: D
Question
d) determine the x-coordinate of the point on the line between the two charges at which the electric potential is zero.
e)how much work must be done by an external force to bring an electron from infinity to the point at which the electric potential is zero? Explain reasoning.
AP* Physics B: Electrostatics Name: Period: Two point charges, q1 and q2, are placed 0.30 m apart on the x-axis, as shown in the figure above. Charge q1 has a value of-3.0 Times 10-9 C. The net electric field at point P is zero. What is the sign of charge q2? Positive Negative Justify your answer. Calculate the magnitude of charge q2. Calculate the magnitude of the electric force on q2 and indicate its direction.Explanation / Answer
B) Because P is on the left, where E is zero, q2 which is on right of P must be positive. We have
{(3.0*10^-9)/(0.1^2)} = {q2/(0.4^2)] or
q2 = 16*3.0*10^-9 C or 4.8*10^-8 C
C)F = (9*10^9)*{(3*4.8)*10^-17}*[1/(0.3^2)} = 1.44*10^-9 N towards q1 or in the direction of negative x axis.
D) Let the required point have the coordinate x. We have
3/(x+0.1) = 48/(0.2 - x) or 48/(x-0.2) OR
16x + 1.6 = 0.2 - x or x - 0.2 OR
17x = -1.4 or 15x = -1.8 OR
x = -1.4/17 = -0.08 m; or x = - 0.6/5 = -0.12 m
E) Required work done is zero. Electric field will support the movement in some region and oppose in some other region so that the net work don will be zero.
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