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CH21
Start Date:
5 Jan 2009 at 01:00 PM
Due Date:
14 Jan 2009 at 11:00 PM
Student Access after Due Date:
Graded:
Yes. View With Assistance
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*Chapter 21, Problem 8 GO
In the figure four particles form a square with edge length a = 4.99 × 10-2 m. The charges are
q1 = q4 = 2.14 × 10-15 C and q2 = q3 = q. What is q (in Coulombs) if the net electrostatic force on particle 1 is zero?
Number
Units
the tolerance is +/-5%
*Chapter 21, Problem 12 GO
The figure shows four identical conducting spheres that are actually well separated from one another. Sphere W (with
an initial charge of zero) is touched to sphere A and then they are separated. Next, sphere W is touched to sphere B
(with an initial charge of -34e) and then they are separated. Finally, sphere W is touched to sphere C (with an initial
charge of 52e), and then they are separated. The final charge on sphere W is 14e. What multiple of e gives the initial
charge on sphere A?
Number
Units
the tolerance is +/-5%
*Chapter 21, Problem 17 GO
The charges and coordinates of two charged particles held fixed in an xy plane are
q1 = 2.61 μC, x1 = 2.89 cm, y1 = 0.204 cm and q2 = -6.37 μC, x2 = -1.64 cm, y2 = 1.01 cm. At what (a)x and (b)y
coordinates should a third particle of charge q3 = 4.91 μC be placed such that the net electrostatic force on particle 2
due to particles 1 and 3 is zero?
(a) Number
Units
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(b) Number
Units
Answer a1: the tolerance is +/-5%
Answer b1: the tolerance is +/-5%
*Chapter 21, Problem 33 GO
In the figure particles 2 and 4, of charge –e, are fixed in place on a y axis, at y2 = -8.70 cm and y4 = 3.91 cm.
Particles 1 and 3, of charge –e, can be moved along the x axis. Particle 5, of charge +e, is fixed at the origin. Initially
particle 1 is at x1 = -11.3 cm and particle 3 is at x3 = 11.3 cm. To what x value must particle 1 be moved to rotate
the direction of the net electric force
Number
net
on particle 5 by 34.6 ˚ counterclockwise?
Units
the tolerance is +/-5%
*Chapter 21, Problem 35
In crystals of the salt cesium chloride, cesium ions Cs+ form the eight corners of a cube and a chlorine ion Cl- is at
the cube's center (Fig. below). The edge length of the cube is L = 0.42 nm. The Cs+ ions are each deficient by one
electron (and thus each has a charge of +e), and the Cl- ion has one excess electron (and thus has a charge of -e).
(a) What is the magnitude of the net electrostatic force exerted on the Cl- ion by the eight Cs+ ions at the corners of
the cube? (b) If one of the Cs+ ions is missing, the crystal is said to have a defect; what is the magnitude of the net
electrostatic force exerted on the Cl- ion by the seven remaining Cs+ ions?
(a) Number
Units
(b) Number
Units
Answer a1: the tolerance is +/-5%
Answer b1: the tolerance is +/-5%
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*Chapter 21, Problem 52
Flying Circus of Physics
If a cat repeatedly rubs against your cotton slacks on a dry day, the charge transfer between the cat hair and the
cotton can leave you with an excess charge of -5.00 μC. (a) How many electrons are transferred between you and the
cat? You will gradually discharge via the floor, but if instead of waiting, you immediately reach toward a faucet, a
painful spark can suddenly appear as your fingers near the faucet. (b) In that spark, do electrons flow from you to
the faucet (type 1) or vice versa (type 0)? (c) Just before the spark appears, do you induce positive (type 1) or
negative (type 0) charge in the faucet? (d) If, instead, the cat reaches a paw toward the faucet, which way do
electrons flow in the resulting spark (from faucet to the cat - type 1, or vice versa - type 0)?
(a)
(b)
(c)
(d)
Answer
Answer
Answer
Answer
a1: the tolerance is +/-5%
b1: exact number, no tolerance
c1: exact number, no tolerance
d1: exact number, no tolerance
*Chapter 21, Problem 59
Three charged particles form a triangle: particle 1 with charge Q1 = 90.0 nC is at xy coordinates (0, 4.80 mm),
particle 2 with charge Q2 is at (0, -4.80 mm), and particle 3 with charge q = 24.0 nC is at (5.60 mm, 0). What are
the x component and y component of electrostatic force on particle 3 due to the other two particles if Q2 is equal to
(a),(b) 90.0 nC and (c),(d) -90.0 nC, respectively?
(a) Number
Units
(b) Number
Units
(c) Number
Units
(d) Number
Units
Answer
Answer
Answer
Answer
a1: the tolerance is +/-5%
b1: the tolerance is +/-5%
c1: the tolerance is +/-5%
d1: the tolerance is +/-5%
Test Bank, Question 1
The charge on a glass rod which has been rubbed with silk is called positive:
by arbitrary convention
so that the proton charge will be positive
to conform to the conventions adopted for G and m in Newton's law of gravitation
because like charges repel
because glass is an insulator
Test Bank, Question 10
A neutral metal ball is suspended by a string. A positively charged insulating rod is placed near the ball, which is
observed to be attracted to the rod. This is because:
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the ball becomes positively charged by induction
the ball becomes negatively charged by induction
the number of electrons in the ball is more than the number in the rod
the string is not a perfect insulator
there is a rearrangement of the electrons in the ball
Test Bank, Question 19
A charged insulator can be discharged by passing it just above a flame. This is because the flame:
warms it
dries it
contains carbon dioxide
contains ions
contains more rapidly moving atoms
Test Bank, Question 30
Two identical conducting spheres A and B carry equal charge. They are separated by a distance much larger than their
diameters. A third identical conducting sphere C is uncharged. Sphere C is first touched to A, then to B, and finally
removed. As a result, the electrostatic force between A and B, which was originally F, becomes:
F/2
F/4
3F/8
F/16
0
Test Bank, Question 40
Two particles, each with charge Q, and a third particle, with a charge q, are placed at the vertices of an equilateral
triangle as shown. The total force on the particle with charge q is:
Parrallel to the left side of the triangle
Parrallel to the right side of the triangle
Parrallel to the bottom side of the triangle
perpendicular to the bottom side of the triangle
perpendicular to the left side of the triangle
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Chapter 21, Concept Question 7
In the figure, a central particle of charge –q is surrounded by two circular rings of charged particles. What are the
magnitude and direction of the net electrostatic force on the central particle due to the other particles? (Hint:
Consideration of symmetry can greatly reduce the amount of work required here.)
upward
downward
leftward
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