Ch. 22 Physics Electrostatics

Important facts about atoms

1. every atom is composed of a positively charged nucleus surrounded by negatively charged atoms. 2. the electrons of all atoms are identical. Each has the same quantity of negative charge and the same mass. 3. Protons and neutrons make up the nucleus. (Only the hydrogen atom, has no neutron, is the only exception) Protons are about 1800 times more massive than electrons. Neutrons have slightly more mass than protons and have no net charge. 4. Atoms usually have as many electrons as protons, so the atom has zero net charge.

Negative Ion

an atom with one or more extra electrons, negatively charged

electric field

an energetic aura that extends through space

Insulators

are tightly bounded and belong to particular atoms. They aren't free to wander about among other atoms in the material.

What is the sign of the charge of the particle in this case?

Positive.

Semiconductor

behave sometimes like an insulator and other times like a conductor.

Compare and contrast Coulombs law to Newtons law

both are inverse-square laws. difference is that gravitation is only attractive wheres electrical forces can repel

What kind of charging occurs during a thunderstorm?

charging by induction

What is a transistor made of and what are some of its functions

composed of thin layers of semiconducting materials. functions- are controlling the flow electrons, amplifying signals, and controlling the switch

How is the direction of the electric field defined?

direction of force on a positive charge

Positive Ion

has a net positive charge

gravitational field

the altered space surrounding a massive body

Conductor

the electrons in the outer atomic shell of its atoms are "loose." Ex. Copper, aluminum, silver, gold, platinum

electrical potential energy

the energy the particle possesses by virtue of its location

Superconductor

the materials acquire zero resistance to the flow of charge

Why is glass and rubber such good insulators?

their strong hold on their electrons

electric dipoles

there is a little more negative charge on one side of the molecule than on the other. Ex. H2O

What is most commonly the net charge of an atom?

zero

Figure 22.5

Although the electrical potential (voltage) of the charged balloon is high, the electric potential energy is low because of the small amount of charge. Therefore, very little energy transfers when the balloon is discharged.

Name one particle that has exactly one particle that has exactly one quantum unit of charge

An electron or proton

Which force binds atoms together to form molecules? A. Nuclear B. Electrical C. Gravitational D. None of these E. Centripetal

Electrical

Conservation of Charge

Electrons are simply transferred from one material to another.

In an electrically neutral atom the number of protons in the nucleus is equal to the number of A. Neutrons in the nucleus B. Electrons that surround the nucleus C. Choices A and B are both incorrect D. Choices A and B are both correct

Electrons that surround the nuclues

Two charged particles repel each other with a force F. If the charge of one of the particles is doubled and the distance between them is also doubled, then the force will be A. 2 F B. F/4 C. F D. F/;2 E. None of these

F/;2

Charging by induction

Fig. 22.7 22.8 and 22.9 is an example

Why does the negative rod in fig 22.7 have the same charge both before and after the spheres are charged, but not when charging takes place as in Figure 22.8?

In the charging process of fig 22.7 no contact was made between the negative rod and either of the spheres. In fig 22.8, however, the rod touched the positively charged sphere. A transfer of charge by contact reduced the negative charge on the rod.

If a proton at a particular distance from a charged particle is repelled with a given force, by how much will the force decrease when the proton is three times father away from the particle? When it is five times farther away?

It decreases to 1/9 its original value; to 1/25 its original value.

In a humorous vein , if you rub a balloon on your hair and put your head to the wall, will it stick to the wall like the balloon would.

It would, if you were and air head--that is, if the mass of your head were about that of the balloon, so that the force produced would be evident.

Beneath the complexities of electrical phenomena, there lies a fundamental rule from which nearly all other effects stem. What is this fundamental rule?

Like charges repel;opposite charges attract

electrically polarized

One side of the atom or molecule is induced into becoming more negative than the opposite side.

When the distance between two charges is halved, the electrical force between the charges A. None of the above choices are correct B. doubles C. halves D. is reduced by 1/4 E. Quadruples

Quadruples

How does the charge of an electron differ from the charge of a proton?

The charge of an electron is equal in magnitude, but opposite in sign, to the charge of a proton.

Which part of an atom is positively charged, which is negatively?

The nucleus and the protons are positively charged and the electtrons are negatively charger

A negatively charged rod is brought close to some small pieces of neutral paper. The positive sides of the molecules in the paper are attracted to the rod and the negative sides of the molecules are repelled. Why don't these attractive and repulsive forces repel?

The positive sides are simply closer to the rod. They therefore experience a greater electrical force than the farther away negative sides. Hence we say that closeness wins. can you see that a positive rod would still produce attraction.

The proton that is the nucleus of hydrogen atom attracts the electron that orbits it. Relative to this force does the electron attract the proton with less force, with more force, or with the same amount of force?

The same amount of force, in accord with Newtons third law--basic mechanics! Recall that a force is an interaction between two things-- in this case, between the proton and electron. They pull on each other equally.

Would the charges induced on spheres A and B of figure 22.7 necessarily be exactly equal and opposite?

Yes because each positive charge on the sphere A results from an electron taken from A and moved to B. This is like removing bricks from the surface of a brick road and placing them all on the sidewalk. The number of bricks on the sidewalk exactly matches the number of holes in the road. Likewise, the number of extra electrons on B will exactly match the number of "holes" left in A. The positive charge is a result of an absent electron.

If you scuff electrons onto your feet while you walk across a rug, are you negatively or positively charged?

You have more electrons after you scruff your feet, so you are negatively charged ( and the rug is positively charged)

What is the net charge of a charged capacitor?

Zero, because the charges on its two plates are equal in number and opposite in sign. Even when the capacitor is discharged--say, by providing a path for charge flow between the oppositely charged plates--the net charge of the capacitor remains zero because then each plate has zero charge.

The unit of electric charge, the coulomb, it the charge on A. a nuetron B. a quark C. a specific large number of electrons D. a specific number of neutrons E. one electron

a specific large number of electrons

Electrostatics

electricity at rest

Why is charge usually transferred by electrons rather than by protons

electrons are loosely bound outside the atoms, whereas protons are very tightly bound within the atomic nuclei

what happens to electrons in any charging process?

electrons are transferred from one place to another

Coulumbs law

for two charged objects that are much smaller than the distance between them, the force between the two objects varies directly as the product of their charges and inversely as the square of the separation distance. The force acts along a straight line from one charged object to the other.

difference between electrically polarized and charged objects?

polarized object may have no net charge

Why do clothes often cling together after tumbling in a clothes dryer?

when electrons from one garment of one material are rubbed onto another material. If the materials were good conductors the discharge between materials would soon occur. But the clothes are nonconducting and the charge for oppositely charged garments to be electrically attracted and stick to one another