1. Two point charges, +25 C and 14 C, are 30 cm apart. a) What force is exerted

ID: 1587463 • Letter: 1

Question

1. Two point charges, +25 C and 14 C, are 30 cm apart.

a) What force is exerted on the negative charge by the positive charge?

b) What electric field is created by the negative charge at the location of the positive charge?

Specify both magnitude and direction.

c) Where, if anywhere, is the total electric field made by the two charges equal to zero?

2. At a particular point in space P, the electric field has a strength of 1.25 x 105 N/C and it is

pointed due north.

a) What is the force exerted by this field on an electron located at point P? Specify both

magnitude and direction.

b) What is the force exerted by this field on a point charge of +40 C located at point P?

Specify both magnitude and direction.

c) Suppose this field is created by a single point charge of 150 C. Where is that point

charge located?

q1 = 25 x 10-6 C

q2 = - 14 x 10-6 C

r = distance between charge particles = 30 cm = 0.30 m

F = force on the negative charge = k q1 q2 /r2 = (9 x 109) (25 x 10-6 ) (14 x 10-6 ) /(0.30)2 = 35 N

Electric field by negative charge is given as

E = k q2/r2 = (9 x 109) (14 x 10-6 ) /(0.30)2 = 1.4 x 106 N/C

let the point be distance "d" from the negative charge

d = distance from charge "q2"

r + d = distance from charge "q1"

for the net electric field to be 0

E1 = E2

k q1 / (r + d )2 = k q2 / d2

25 x 10-6 / (0.30 + d)2 = 14 x 10-6 /d2

d = 0.892 m

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