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Physics 121 Practice Problem Solutions 02 Electric Charge: Contents

This document contains solutions to practice problems about electric charge from a Physics 121 course. It addresses topics like Coulomb's law, electrostatic force between point charges, components of net electrostatic force, equilibrium of charged particle systems, maximizing electrostatic repulsion between two charges, and the separation between identically charged conducting balls hanging from threads for equilibrium. The problems involve calculating forces, locations, and charges using equations relating charge, distance, and electrostatic force.

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H Aries Oña
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301 views8 pages

Physics 121 Practice Problem Solutions 02 Electric Charge: Contents

This document contains solutions to practice problems about electric charge from a Physics 121 course. It addresses topics like Coulomb's law, electrostatic force between point charges, components of net electrostatic force, equilibrium of charged particle systems, maximizing electrostatic repulsion between two charges, and the separation between identically charged conducting balls hanging from threads for equilibrium. The problems involve calculating forces, locations, and charges using equations relating charge, distance, and electrostatic force.

Uploaded by

H Aries Oña
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Physics 121 Practice Problem Solutions 02

Electric Charge
Contents:
121P02 -1P, 2P, 5P, 9P, 10P, 13P, 15P

• History
• Electromagnetism
• Electric Charge
• Quantization of Charge
• Structure of Matter
• Conductors and Insulators
• Conservation of Charge
• Coulomb’s Law – Force
• Shell Theorem
• Examples

1
Fall 2012
PROBLEM 121P02- 1P: What must be the distance between point charge q1 = 26.0 µC and
point charge q2 = -47.0 µC for the electrostatic force between them to have a magnitude of
5.70 N?

Fall 2012
PROBLEM 121P02 - 2P*: A point charge of +3.00 x 10-6 C is 12.0 cm distant from a second
point charge of -1.50 x 10-6 C. Calculate the magnitude of the force on each charge.

Fall 2012
PROBLEM 121P02 - 5P: In the figure , what are the (a) horizontal and (b) vertical
components of the net electrostatic force on the charged particle in the lower left corner of
the square if q = 1.0x10-7 C and a = 5.0 cm?

Fall 2012
PROBLEM 121P02 - 9P: Two free particles (that is, free to move) with charges +q and +4q
are a distance L apart. A third charge is placed so that the entire system is in equilibrium.
(a) Find the location, magnitude, and sign of the third charge. (b) Show that the
equilibrium is unstable.

Fall 2012
PROBLEM 121P02 - 10P*: Two fixed particles, of charges q1 = +1.0 µC and q2 = -3.0 µC,
are 10 cm apart. How far from each should a third charge be located so that no net
electrostatic force acts on it?

Fall 2012
PROBLEM 121P02 - 13P*: A certain charge Q is divided into two parts q and Q - q, which
are then separated by a certain distance. What must q be in terms of Q to maximize the
electrostatic repulsion between the two charges?

Fall 2012
PROBLEM 121P02 - 15P: In the figure, two tiny conducting balls of identical mass m and identical charge
q hang from nonconducting threads of length L. Assume that θ is so small that tan θ can be replaced by its
approximate equal, sin θ. (a) Show that, for equilibrium,

where x is the separation between the balls. (b) If L = 120 cm, m = 10 g, and x = 5.0 cm, what is q?

Fall 2012

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