<< Chapter < Page Chapter >> Page >

As the example implies, gravitational force is completely negligible on a small scale, where the interactions of individual charged particles are important. On a large scale, such as between the Earth and a person, the reverse is true. Most objects are nearly electrically neutral, and so attractive and repulsive Coulomb forces nearly cancel. Gravitational force on a large scale dominates interactions between large objects because it is always attractive, while Coulomb forces tend to cancel.

Test prep for ap courses

For questions 25–27, suppose that the electrostatics force between two charges is F .

What will be the force if the distance between them is halved?

  1. 4 F
  2. 2 F
  3. F /4
  4. F /2

(a)

Got questions? Get instant answers now!

Which of the following is false?

  1. If the charge of one of the particles is doubled and that of the second is unchanged, the force will become 2 F .
  2. If the charge of one of the particles is doubled and that of the second is halved, the force will remain F .
  3. If the charge of both the particles is doubled, the force will become 4 F .
  4. None of the above.
Got questions? Get instant answers now!

Which of the following is true about the gravitational force between the particles?

  1. It will be 3.25×10 −38 F .
  2. It will be 3.25×10 38 F .
  3. It will be equal to F .
  4. It is not possible to determine the gravitational force as the masses of the particles are not given.

(d)

Got questions? Get instant answers now!

Two massive, positively charged particles are initially held a fixed distance apart. When they are moved farther apart, the magnitude of their mutual gravitational force changes by a factor of n . Which of the following indicates the factor by which the magnitude of their mutual electrostatic force changes?

  1. 1/ n 2
  2. 1/ n
  3. n
  4. n 2
Got questions? Get instant answers now!
  1. What is the electrostatic force between two charges of 1 C each, separated by a distance of 0.5 m?
  2. How will this force change if the distance is increased to 1 m?

(a) 3.60×10 10 N, (b) It will become 1/4 of the original value; hence it will be equal to 8.99×10 9 N

Got questions? Get instant answers now!
  1. Find the ratio of the electrostatic force to the gravitational force between two electrons.
  2. Will this ratio change if the two electrons are replaced by protons? If yes, find the new ratio.
Got questions? Get instant answers now!

Section summary

  • Frenchman Charles Coulomb was the first to publish the mathematical equation that describes the electrostatic force between two objects.
  • Coulomb's law gives the magnitude of the force between point charges. It is
    F = k | q 1 q 2 | r 2 , size 12{F=k { {q rSub { size 8{1} } q rSub { size 8{2} } } over {r rSup { size 8{2} } } } } {}

    where q 1 and q 2 are two point charges separated by a distance r , and k 8.99 × 10 9 N · m 2 / C 2

  • This Coulomb force is extremely basic, since most charges are due to point-like particles. It is responsible for all electrostatic effects and underlies most macroscopic forces.
  • The Coulomb force is extraordinarily strong compared with the gravitational force, another basic force—but unlike gravitational force it can cancel, since it can be either attractive or repulsive.
  • The electrostatic force between two subatomic particles is far greater than the gravitational force between the same two particles.

Conceptual questions

[link] shows the charge distribution in a water molecule, which is called a polar molecule because it has an inherent separation of charge. Given water's polar character, explain what effect humidity has on removing excess charge from objects.

A schematic representation of the outer electron cloud of a neutral water molecule is shown. Three atoms are placed on the vertices of a triangle. The hydrogen atom has positive q charge and the oxygen atom has minus two q charge, and the angle between the line joining each hydrogen atom with the oxygen atom is one hundred and four degrees. The cloud density is shown more at the oxygen atom.
Schematic representation of the outer electron cloud of a neutral water molecule. The electrons spend more time near the oxygen than the hydrogens, giving a permanent charge separation as shown. Water is thus a polar molecule . It is more easily affected by electrostatic forces than molecules with uniform charge distributions.

Got questions? Get instant answers now!

Questions & Answers

summarize halerambos & holbon
David Reply
the Three stages of Auguste Comte
Clementina Reply
what are agents of socialization
Antonio Reply
sociology of education
Nuhu Reply
definition of sociology of education
Nuhu
what is culture
Abdulrahim Reply
shared beliefs, values, and practices
AI-Robot
What are the two type of scientific method
ogunniran Reply
I'm willing to join you
Aceng Reply
what are the scientific method of sociology
Man
what is socialization
ogunniran Reply
the process wherein people come to understand societal norms and expectations, to accept society's beliefs, and to be aware of societal values
AI-Robot
scientific method in doing research
ogunniran
defimition of sickness in afica
Anita
Cosmology
ogunniran
Hmmm
ogunniran
list and explain the terms that found in society
REMMY Reply
list and explain the terms that found in society
Mukhtar
what are the agents of socialization
Antonio
Family Peer group Institution
Abdulwajud
I mean the definition
Antonio
ways of perceived deviance indifferent society
Naomi Reply
reasons of joining groups
SAM
to bring development to the nation at large
Hyellafiya
entails of consultative and consensus building from others
Gadama
World first Sociologist?
Abu
What is evolutionary model
Muhammad Reply
Evolution models refer to mathematical and computational representations of the processes involved in biological evolution. These models aim to simulate and understand how species change over time through mechanisms such as natural selection, genetic drift, and mutation. Evolutionary models can be u
faruk
what are the modern trends in religious behaviours
Selekeye Reply
what are social norms
Daniel Reply
shared standards of acceptable behavior by the group or appropriate behavior in a particular institution or those behaviors that are acceptable in a society
Lucius
that is how i understood it
Lucius
examples of societal norms
Diamond
Discuss the characteristics of the research located within positivist and the interpretivist paradigm
Tariro Reply
what is Industrialisation
Selekeye Reply
industrialization
Angelo
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply
Practice Key Terms 3

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, College physics for ap® courses. OpenStax CNX. Nov 04, 2016 Download for free at https://legacy.cnx.org/content/col11844/1.14
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'College physics for ap® courses' conversation and receive update notifications?

Ask