Physics Ch 8

When you remove a wool dress from a garment bag, the sides of the bag might tend to stick to the dress. Explain.

Because of friction, bag and dress becomes opposite charge causing them to attract each other

Give evidence supporting the claim that most of an atom's mass is concerned in a tiny nucleus at the center

Experiment form Rutherford and Marsden. They aimed energetic alpha particles produced by radioactive decay at gold foil.

What happens to the electric force between two charged objects if the charges on both of them is reversed in sign?

Force remain the same

Suppose that electric force between 2 objects is 2 N and that you then double the electric charge on each object. What is the new force?

New force between to objects is 8N

Suppose that electric force between 2 objects is 2 N and that you then double the distance between objects. What is the new force?

New force when you double the distance between the objects is .50N

Does more current flow out of a battery than into it?

No, the current flow out of battery is not more than into it.

What is an electric current?

a flow of charged particles

if you place a proton at some point in an electric field and then release it, what will happen?

proton will accelerate in the direction of electric field

List the types of particles that are found within the atom

protons, electrons, neutrons

What holds, or binds, an atom's orbiting electrons to the nucleus?

the atomic nucleus is positively charged from the protons and the force o electrical attraction its electric charge exert on the negatively charged electrons keeps the electrons in orbiting and bind them.

What happens to the electric force between two charged objects if the charge on one of them is reversed in sign?

the force between them is reversed with the magnitude of the force remaining the same. The direction of forces reverses because changing one sign makes charge of opposite attract.

Objects A and B are both electrically charged. If the distance between them is halved while the charge on A is also halved, what happens to the force between them?

the new force is twice as large

You have 3 iron bars, only two of which are permanent magnets. because of temporary magnetization, all three bars at first appear to be magnetized. how can you determine which one is magnetized, without using any other objects?

When two bars that repel each other in some orientation are found these are the two magnetized. Choose one bar and hold an end of the second bar near its end to see whether the bars attract or repel.

If the distance between two charged objects is reduced one-fourth of its original value, what happens to the electric force between them?

the force between them is multiplied by 16

A proton is placed, at rest, at some point A within a room that is otherwise devoid of all matter. At some other point B withing the room is there an electric field? An electric force? A magnetic field? a magnetic force? is there energy at point B?

there will be electrical field at point B due to proton. It's because of electric field at point B there is energy at point B

suppose you have a piece of metal wire and permanent magnets. describe two ways in which you could create an electric current. what law of physics is involved here?

1. Move the magnetic pole toward or even into the loop 2. move the loop into the magnet * Faraday's Law

Describe at least 2 ways in which the gravitational force and the electric force differ.

1. The electric force between two charges can be either force of repulsion or force of attraction, while gravitational force between two masses is always force of attraction. 2. electric force is generally stronger than gravitational force because gravitational attraction is requires objects of very large mass.

Name two kinds, of force fields

Gravitational field and electromagnetic field

Do the headlights of an automobile carry AC or DC? What about a toaster in your kitchen?

Headlight carries DC.They are powered by battery, has the same positive and negative terminals. Toaster operates AC because the electric energy provided by electrical utilities to household wiring is almost always alternating current.

Is a wire that carries current electrically charged?

No, the wire carrying the current is electrically neutral

If the distance between two charged objects and the charge on each of them are all doubled, what happens to the electric force between them?

The force is the same as before

Ping pong ball A has an electric charge that is 10 times larger than the charge on ping pong ball B. When placed sufficiently close together to exert measurable electric forces on each other, how does the force by A on B compare with the force by B on A?

The force that A exert on B is equal in magnitude and opposite in direction to the force that B exert on A

what is the effect on the motions of a moving electron and a moving proton that move into a magnetic field (that is not oriented in the direction of motion of the two particles) how do the motions of the two particles differ?

They will move apart towards the opposite end of the field.

Do the electric circuits in your home produce magnetic fields? Suggest a measurement that might check your answer.

Yes because net motion of electric charge. Bringing unmagnified iron near wiring produce a magnetic force on iron, but maybe weak to detect easily.

how would a proton's motion differ from the motion of an electron placed at the same point in the same gravitational field?

because proton has larger mass it experiences a greater force of gravity in proportion to its mass. But this cancel because of newton's second law. Acceleration of proton and electron will be the same independent of mass, and both will move in the same way.

Highway trucks can become electrically charged as they travel. How can this happen? This can be dangerous, especially for gasoline tank trucks. How can it be prevented?

because the surfaces of tires and the road that come in contact are made of different materials so that electrons from one surface can transfer to the other surface, depends on which attaches the electrons better. Trucks often have a conducting strap or chain dragging on the ground to allow charge to flow between the truck body and ground.

how would a proton's motor differ from the motion of an electron placed at the same point in the same electric field?

electron is negative charge, therefore it would experience an electric force in the opposite direction from the force that a proton would experience. Therefore, it would accelerate in the opposite direction of protons

Which force fields would be felt by a moving uncharged object: gravitational, electric, or magnetic?

gravitational field

Which force fields would be felt by a stationary charged object: gravitational, electric, or magnetic?

gravitational field and electric field

Which force fields would be felt by a moving charged object: gravitational, electric, or magnetic?

gravitational field and magnetic field and electric fiel

Some science fiction stories portray atoms as true miniature solar systems populated by tiny creatures. What are some differences, other than size, between our solar system and the planetary model of an atom?

gravitational forces are always attractive while electrical forces can be attractive or repulsive, depends on sign. As a result, planets moving around the sun exert only forces of attraction on each other, while electron repel each other but attracted to nucleus.

is an electric field a form of matter? explain. what about gravitational field?

here an electrical field is not made up of atoms or other material particles. Thus it is not a form of matter. Same as gravitational field.

Since matter is made of electrically charged particles, why don't we and the objects around us feel electric forces all the time?

in any small region of space, negative and positive charges are balanced in equal amount. Thus, there is no electric force except at microscopic level.

What is an ion?

ion is an atom that has net charge because it mas more electrons than protons or fewer electrons than protons.

suppose you have 2 iron bars (see the previous exercise), one magnetized and one not magnetized. can you then determine which one is magnetized, without using any other objects?

its not possible to determine which one of the to iron bars is magnetized by holding them end to end at their poled because they will always attract that way regardless of which one is magnetized.

Suppose that you rub a transparency with a tissue to charge both objects and then hold them several meters apart and shake both of them back and forth . Name the forces that they exert on each other.

magnetic and electric and very very small gravitational force

Magnetic forces are always caused by what types of objects?

moving electrical charged objects or particles

After you walk across a rug and scuff electrons off the rug, are you positively or negatively charged?

negatively charged

Which types of particles within the atom are electrically charged?

protons and electrons

While brushing your hair, you find that the hairs tend to stand apart from one another and that they are attracted toward the brush. Explain this in microscopic terms.

while brushing your hair, electrons are rubbed off the brush into the hair or vice versa. Every hair consists the same charge hence they repel each other. While brush, carries differ kind of charge, so brush attracts each hair.