This question has several parts that must be completed sequentially. If you skip

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This question has several parts that must be completed sequentially. If you skip a part of the question, you will not receive any points for the skipped part, and y will not be able to come back to the skipped part Tutorial Exercise Two point charges Q1 - +5.55 nC and 2--3.05 nc are separated by 40.0 cm. (a) What is the electric potential at a point midway between the charges? (b) What is the potential energy of the pair of charges? what is the signifcance of the algebraic sign of your answer? Step 1 (a) The point midway between the charges is located at a distance of r1 = r2 = (40.0 cm)/2 . 20.0 cm, where r1 and r2 are the distances to this midway point from each charge Qs and Q2, respectively. The electric potential at this point is the algebraic sum of the two contributions, one from each charge. Note that it is important to include the signs of the charges in the equation below 10-9 x 10-9 c -(8.99x10 N m2/c2 v. Need Help? Read t

Explanation / Answer

The electrical potentials add algebraically; taking into account thesign of the charges.

Hence, at the mid point, at a distance of 40/2 = 20 cm = 0.2 m,

the total potential is givn by,

                       V = k(q1- q2)/d/2

                          = 9x109x(5.55 -3.05)x10-9 / 0.2

                           = 9 x 2.5 /0.2

                             = 112.5 V  

(b) The el potential energy of the pair,

(r is the distance between the pair, 40 cm = 0.4 m)

                 UE = kq1.q2/r = -9x109 x 5.55x3.05x 10-18/0.4

                     = -380x10-9 J = -3.8x10-7 J

The negative sign implies that positive work must be done toseparate these charges.

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