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1. A positive charge q moves in the direction of an electric field, pointing fro

ID: 2001587 • Letter: 1

Question

1. A positive charge q moves in the direction of an electric field, pointing from A to B. Which point in space has a higher electric potential, A or B? Explain.

2. Six point charges (each with charge -2Q) are placed uniformly around a circle with radius R. What is the electric potential at the center of the circle?

3. Show a configuration of the point charges q, 2q, 3q along the x-axis so that the electric potential at the origin is 13keq/3r

4. A point charge +Q lies at the origin and another point charge -2Q lies at x=D along the x-axis. At what point along the x-axis is the electric potential zero?

Explanation / Answer

1. A is at higher potential because, because potential decreases as you move along in the direction of the electric field.

2. V = K(q1/r1 + q2/r2 ............. + q6/r6)

therefore, V = -12KQ/R

3. q and 3q at a x = 1 and -1 respectively and 2q at x = r/6.

4. Let the potential is zero d distace away from origin and D>0;(let d be on positive x axis and <D)

Q/d = 2Q/(D-d)

d = D/3 (on positive x axis)

now, let d be on positive x axis and >D

Q/d = 2Q/(d-D)

no such value of d is possible.

now, let d be on negative x axis.

Q/d = 2Q/(d+D)

d = D. (on negative x axis)