KFUPM-Physics102-052

Dr.Aljalal

Sec16

Sec17

Sec18

Recitation ch 21

Answers at the end

Question 1

Two point charges q1 and q2 lie along the x-axis.

q1 = + 16.0 micro-Coulombs is at x = 2.00 m and

q2 = + 9.00 micro-Coulombs is at the origin.

Where must a negative charge q3 be placed on

the x-axis such that the net electrostatic force

on it is zero ?

a x = + 1.14 m

b x = - 1.14 m

c x = + 0.857 m

d x = - 0.857 m

e x = + 2.86 m

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Question 2

As in figure (1), a charge Q is fixed at each of two opposite

corners of a square. A charge q is fixed at each of the other

two corners. If the resultant electrical force on Q is zero,

then Q and q are related as:`

a Q = - 2 Sqrt(2) q**2

b Q = q

c Q = - 2 Sqrt(2) q

d Q = q**2

e Q = - 4 q

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Question 3

Two fixed particles, of charges q1 = + 1.0*10**(-6) C and q2=

- 9.0*10**(-6) C, are 10 cm apart. How far from each should

a third charge be located so that no net electrostatic force

acts on it?

a 1 cm from q1 and 11 cm from q2.

b 5 cm from q1 and 15 cm from q2.

c 3 cm from q1 and 7 cm from q2.

d 1 cm from q1 and 9 cm from q2.

e 1.1 cm from q1 and 11.1 cm form q2.

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Question 4

Consider two identical conductor spheres, A and B.

Initially, sphere A has a charge of -80 Q and Sphere B

has a charge of +20 Q. If the spheres touched and then

are separated by a distance of 0.3 m, what is the

resultant force between them? [Take Q = 5.7*10**(-8) C]

a 0.2 N.

b 0.3 N.

c 0.4 N.

d 0.6 N.

e 0.9 N.

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Question 5

Charges q1 and q2 are on the x-axis. q1 is at x = a

and q2 is at x = 2a. The net force on a third charge

at the origin is zero.

Which of the following is TRUE ?

a q2 = -4*q1

b q2 = 2*q1

c q2 = -q1

d q2 = 4*q1

e q2 = -2*q1

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Answers

1 c

2 c

3 b

4 b

5 a