Electrostatics1

Conservation of charge means that

-electrons by themselves can be neither created nor destroyed -charge can be neither created nor destroyed -the total amount of charge in the universe is constant -no experimenter has ever seen a single charge destroyed by itself

The electrostatic force between two charges located 8 meters apart is 0.10 N. What will the force be between these charges when they are located 2 meters apart

1.6 N

Two charges separated a distance of 1.0 meter exert a 2.0-N force on each other. If the charges are pushed to a separation of 1/3 meter, the force on each charge will be

18.0 N

A 2-C charge and a 4-C charge attract each other with 10 N of force. How much will a 2-C charge and a 12-C charge attract each other when placed the same distance apart

30 N

Two charges separated by a distance of 1 meter exert a 20-N force on each other. If the charges are pulled to a 2 meter separation distance, the force on each charge will be

5.0 N

Two charges separated by a distance of 1 meter exert a 2-N force on each other. If the magnitude of each charge is doubled, the force on each charge will be

8.0 N

Calculate the electrical force between two electrons that are located on opposite sides of an ionized hydrogen atom. Use the following values for the distance and charge size. distance = 5.3 x 10⁻¹¹ m electron charge = -1.6 x 10⁻¹⁹ C

= 8.2 x 10⁻⁸ N = 8.2 x 10⁻⁸ N

List the similarities and differences between Coulomb's law and Newton's law of gravitation

Both law are inverse- square laws and both are directly dependent on the quantities involved; electric charge for electrical force and mass for gravitational force. The Coulomb force is about 1039 times stronger than the gravitational force. Also, the electrical force may be either attractive or repulsive.

The SI unit of charge is the

Coulomb

What are three ways an object can become charged? How does each work? Give examples

Objects can become charged by friction, contact or induction. In charging by friction, two objects are rubbed together, thereby transferring electrons from one object to the other. In charging by contact charge is also directly transferred from one abject to another object. In charging by induction, one objects momentarily grounded while a charged object is located nearby. Rubbing a rubber rod with cat's fur is an example of charging by friction. Touching the charged rubber rod to an uncharged tin can is an example of charging by contact. Holding a charged rod near a tin can and touching the can with your finger is an example of charging by induction.

Electrical forces between charges are strongest when the charges are

close together

A material is a good insulator if outer electrons of atoms in the material are free to roam around

false

An atom that is electrically polarized vibrates in only one direction

false

A positive charge and a negative charge held near each other are released. As they move, the force on each particle

increases

The reason a charged balloon will stick to a wall is that

induced opposite charges in the wall are closer than other wall charges

Bring a charged object near a conductor and then momentarily touch the conductor. This demonstrates charge by

induction

When a charged cloud passes overhead, the ground below is charged by

induction

Objects can be charged by

induction, friction, and touching (all of the above)

To charge an object by induction, the process of grounding

may or may not occur

A positive ion has

more protons than electrons

An electroscope is charged positively, as shown by foil leaves that stand apart. As a negatively charged rod is brought close to the electroscope, the leaves

move closer together

If you comb your hair and the comb becomes positively charged, your hair becomes

negatively charged

To say that electric charge is conserved means that no case has ever been found where

net charge has been created or destroyed

Two charged particles held close to each other are released. As they move, the force on each particle increases. Therefore, the particles have

opposite signs

A rubbed balloon will stick to a wooden wall, which demonstrates charge

polarization

A negatively charged rod is brought near a metal can that rests on a wood table. You touch the opposite side of the can momentarily with your finger. The can is then

positively charged

Atomic nuclei of almost all elements consist of

protons and neutrons

Two charges are separated by a certain distance. If the magnitude of each charge is doubled, the force on each charge is

quadrupled

When the distance between two charges is halved, the electrical force between the charges

quadruples

Particle A has twice as much charge as particle B. Compared to the force on particle A, the force on particle B is

the same

Two charged particles held near each other are released. As they move, the acceleration of each decreases. Therefore, the particles have

the same sign

In a good insulator, electrons are usually

tightly bound in place

A bolt of lightning is a result of charging by induction

true

A material that is a good insulator of electricity is normally a poor conductor of electricity

true

All electrons are identical; all have exactly the same mass and charge

true

Coulomb's law for electrical charges has the same mathematical form as Newton's law of gravitation

true

How many different kinds of force would act on a proton placed in both an electric field and a gravitational field

two

Coulomb's law says that the force between any two charges depends

directly on the size of the charges and inversely on the square of the distance between the charges or both A & B

The charge of an electron is

negative

Common hydrogen atom consists of

one proton and one electron

Two like charges

repel each other

A difference between electrical and gravitational forces is that electrical forces include

repulsive interactions

To be safe in the unlikely case of a lightning strike, it is best to be inside a building frame with

steel

Semiconductors can be made to conduct electricity and they can also be made to act like good insulators

true

The study of electricity at rest is electrostatics

true

The total amount of charge in the universe is constant. We have never observed a case of net creation or destruction of charge.

true

When we allow charges to move onto or off a conductor by touching it with something connected to Earth, it is common to say that we are grounding it

true

A conductor differs from an insulator in that a conductor has

• NOT more protons than electrons • NOT faster-moving molecules • NOT more electrons than protons • NOT more electrons than an insulator (NONE of the above)

Much electronic equipment contains transistors and diodes that are made from semiconductors. Semiconductors

• can be very good insulators • can conduct electricity • contain helpful impurities (all of the above)

Charge carriers in a metal are electrons rather than protons because electrons are

• relatively far from a a nucleus • loosely bound • lighter (all of the above)

What is the difference between an insulator and a conductor? which would you guess copper is? Wood? Distilled water?

A good electrical conductor is any material composed of atoms with "loose" outer electrons that are freeto move about in the material, such as copper. A good electrical insulator is a material composed ofatoms that tightly bind electrons. Wood and distilled water are examples of good electrical insulators.

Why should you not stand or sit in water when using electrical appliances? Why is it not a good idea to talk to your friend on the phone while sitting in a bath?

Ordinary water is a conductor of current. Therefore, when using a plugged-in electrical device, you shouldnot be standing or sitting in water that is connected to Earth. If a short circuit occurs, you may be part ofthe pathway to the ground. For the same reason it is not a good idea to use the phone while taking a bath(although the voltage and current in a phone are relatively low).

State Coulomb's law. Explain what each symbol in it stands for, and use it to find the force bewteen a -.002-C charge and a 0.006-C charge that are 10 meters apart

The force between two charge depends directly on the magnitude of each charge and inversely on the square of the distance between the charges. [eq1] is the proportionality constant, q1 and q2 are the magnitudes of the charges, d is the distance... The force between two charge depends directly on the magnitude of each charge and inversely on the square of the distance between the charges. [eq1] is the proportionality constant, q₁ and q₂ are the magnitudes of the charges, d is the distance between the charges, and F is the force between the charges. [eq2]

Protons and electrons

attract eachother

Electrical polarization occurs when

charge distribution in a neutral molecule separates

Two charged particles held close to each other are released. As the particles move, the velocity of each increases. Therefore, the particles have

charges that cannot be determined

Lighting bolts occur between

clouds and the ground clouds (both A & B)

The charge distribution in some molecules is permanently separated into positive and negative regions. Such molecules are called

electric dipoles

The fundamental force underlying all chemical reactions is

electrical

Coulomb's law says that the are two kinds of charges, positive and negative

false

Electrical forces are strong, but in comparison, gravitational forces are stronger

false

The reason electrons are attracted to protons ins that electrons and protons have the same amount of charge

false

When an object is charged by contact, electrons flow from the ground onto the object, or from the object onto the ground

false

The net charge of a nonionized atom

is zero