Physics Chapter 20 & 21

A neutral metal sphere is touched by a negatively charged metal rod. As a result, the sphere will be ____ and the metal rod will be ____. Select the two answers in their respective order. a. positively charged b. negatively charged c. neutral d. much more massive e. ... not enough information to tell

B & B

What is the difference between a conductor and insulator in terms of charges?

Conductor: -charge spreads out evenly Insulator: -holds charges where they are placed

TRUE or FALSE: The presence of lightning rods on top of buildings prevents a cloud with a static charge buildup from releasing its charge to the building.

False

Saran Wrap has a larger electron affinity than Nylon. If Nylon is rubbed against Saran Wrap, which would end up with the excess negative charge?

Saran Wrap

grounding

The process of moving excess charge by touching an object to Earth

Explain what a capacitor does and give an example.

-A capacitor stores electrical energy -EX: a computer circuit board uses many capacitors in its operation

Explain the effect of increasing charge and distance has on the electrostatic force between charged objects

-Increasing distance between objects decreases the force of attraction between the objects -Increasing charged results in a larger force

charging by induction

-The process by charging an object without touching it -this can be accomplished by bringing a charged object close to a neutral object, causing a separation of charges, then separating the object to be charged, trapping opposite but equal charges

Electrostatistics

-the study of electric charges that can be collected and held in one place -study of static electricity

What are three applications of static electricity?

1. smokestacks 2. paint droplets 3. photocopy machines

What does one coulomb equal to?

6.24 x 10^-19

electroscope

A device use to detect electric charges and consists of a metal knob connected by a metal stem of two thin metal leaves

A physics teacher rubs a glass object and a felt cloth together and the glass becomes positively charged. Which of the following statements are true? Circle all that apply. a. The glass gained protons during the rubbing process. b. The felt became charged negatively during this rubbing process. c. Charge is created during the rubbing process; it is grabbed by the more charge-hungry object. d. If the glass acquired a charge of +5 units, then the felt acquires a charge of -5 units.

B & D

A metal sphere is electrically neutral. It is touched by a positively charged metal rod. As a result, the metal sphere becomes charged positively. Which of the following occur during the process? List all that apply. *a. The metal sphere gains some protons.,/p.* b. Electrons are transferred from the sphere to the rod. *c. The metal sphere loses electrons.* d. The overall charge of the system is conserved. *e. Protons are transferred from the rod to the sphere.* f. Positive electrons are moved between the two objects.

B, C, & D

A positively charged pop can is touched by a person standing on the ground. The pop can subsequently becomes neutral. The pop can becomes neutral during this process because ______. a. electrons pass from the pop can to the person (ground) b. electrons pass from the person (ground) to the pop can c. protons pass from the pop can to the person (ground) d. protons pass from the person (ground) to the pop can

B. electrons pass from the person (ground) to the pop can

A positively charged piece of Styrofoam is placed on the table. A neutral aluminum pie plate is brought near. While held above the Styrofoam, the aluminum plate is touched (grounded). At this point, there is a movement of electrons. Electrons move... *a. out of the aluminum plate into the ground (hand)* b. into the aluminum plate from the ground (hand) *c. into the aluminum plate from the Styrofoam* d. out of the aluminum plate into the Styrofoam *e. from the ground through the aluminum plate to the Styrofoam* f. from the Styrofoam through the aluminum plate to the ground *g. .... nonsense! Electrons do not move at all.*

B. into the aluminum plate from the ground (hand)

Why does a balloon stick to the wall?

Because the negative charges on the chalkboard move to the opposite dies which means all that is left over is the positive

Explain the behavior of the metallic painted pith ball in the electrophorus.

By rubbing fur on the a styrofoam block, electrons were transferred from the fur to the block and the block became negatively charged. Since the foil had a neutral charge, the objects attracted. The foil gained electrons and had a negative charge. The pith ball, also neutral, was attracted to the foil and obtained a negative charge. Since both the foil and the ball had negative charges, the objects repelled. When my finger, a neutral charge, attracted the ball, my finger gained electrons and the ball repelled. It was then again attracted to the foil and the process repeated over again.

Which statement best explains why a rubber rod becomes negatively charged when rubbed with fur? a. The rubber that the rod is made of is a better insulator than fur. b. The fur is a better insulator than the rubber. c. Molecules in the rubber rod have a stronger attraction for electrons than the molecules in the fur. d. Molecules in the fur have a stronger attraction for electrons than the molecules in the rubber rod.

C. Molecules in the rubber rod have a stronger attraction for electrons than the molecules in the fur.

A neutral metal sphere is touched by a negatively charged metal rod. During the process, electrons are transferred from the _____ to the _____ and the sphere acquires a _____ charge. a. neutral sphere, charged rod, negative b. neutral sphere, charged rod, positive c. charged rod, neutral sphere, negative d. charged rod, neutral sphere, positive e. ... nonsense! None of these describe what occurs.

C. charged rod, neutral sphere, negative

Two neutral conducting pop cans are touching each other. A positively charged balloon is brought near one of the cans as shown below. The cans are separated while the balloon is nearby, as shown. After the balloon is removed the cans are brought back together. When touching again, can X is ____. a. positively charged b. negatively charged c. neutral d. impossible to tell

C. neutral

During a physics lab, a plastic strip was rubbed with cotton and became positively charged. The correct explanation for why the plastic strip becomes positively charged is that A. the plastic strip acquired extra protons from the cotton B. the plastic strip acquired extra protons during the charging process C. protons were created as the result of the charging process D. the plastic strip lost electrons to the cotton during the charging process

D. the plastic strip lost electrons to the cotton during the charging process

The Q in Coulomb's law equation stands for the _____. a. mass of a charged object b. # of excess electrons on the object c. the current of a charged object d. the distance between charged objects e. charge of a charged object

E. charge of a charged object

A physics student, standing on the ground, touches an uncharged plastic baseball bat to a negatively charged electroscope. This will cause *a. the electroscope to be grounded as electrons flow out of the electroscope.* b. the electroscope to be grounded as electrons flow into the electroscope. *c. the electroscope to be grounded as protons flow out of the electroscope.* d. the electroscope to be grounded as protons flow into the electroscope. *e. the baseball bat to acquire an excess of protons.* f. absolutely nothing (or very little) to happen since the plastic bat does not conduct.

E. the baseball bat to acquire an excess of protons.

How does the distance between two charges impact the force between them?If the distance is decreased while the charges remain the same, what happens to the force?

Electric force is inversely proportional to the distance squared. As distance decreases and charges remain the same, the force increases as the square of the distance.

How are electrostatic force and gravitational forces different?

Electrostatic Forces: -the property decreases -requires transmission of electrons -stronger -repulsive or attractive Gravitational Forces: -does no require transmission of electrons -does not decrease -always attractive

TRUE or FALSE: An object that becomes grounded gains neutrons during the grounding process.

False

TRUE or FALSE: If you place a lightning rod on top of your home but failed to ground it, then you home would still be safe in the unlikely event of a lightning strike.

False

TRUE or FALSE? Two neutral conducting pop cans are touching each other. A negatively charged balloon is brought near Can X as shown below. As the balloon approaches Can X, there is a movement of electrons between the balloon and can X (in one direction or the other).

False

A physics teacher rubs a glass object and a felt cloth together and the glass becomes positively charged. Which of the following statements are true? Circle all that apply. e. This event violates the law of conservation of charge. f. Electrons are transferred from glass to felt; protons are transferred from felt to glass. g. Once charged in this manner, the glass object and the felt cloth should attract each other. h. In general, glass materials must have a greater affinity for electrons than felt materials.

G

Two neutral conducting pop cans are touching each other. A positively charged glass rod is brought near Can X as shown below. Which of the following occur as the glass rod approaches Can X? List all that apply. *a. Electrons jump from the glass rod to can X.* b. Electrons jump from the glass rod to can Y. *c. Electrons jump from can X to the glass rod.* d. Electrons jump from can Y to the glass rod. *e. Protons jump from the glass rod to can X.* f. Protons jump from can X to the glass rod. *g. ... nonsense! None of these occur.*

G. nonsense! None of these occur

List some insulators and conductors.

Insulators: -air -wood -plastic -glass -cloth Conductors: -metals

What property makes metal a good conductor and rubber a good insulator?

Metals contain free electrons; rubber has bound electrons.

Can charged objects repel neutral objects?

No, charged objects will not repel neutral objects

Can neutral objects attract neutral objects?

No, neutral objects will not attract neutral objects

The combined charge of all electrons in a nickel is hundreds of thousands of coulombs. Does this imply anything about the net charge on the coin? Explain.

No. Net charge is the difference between positive and negative charges. The coin still can have a net charge of zero.

If you wipe a compact disc with a clean cloth, why does the CD then attract dust?

Rubbing the CD charges it. Neutral particles, such as dust, are attracted to a charged object.

After a comb is rubbed on a wool sweater, it is able to pick up small pieces of paper. Why does the comb lose that ability after a few minutes?

The comb loses its charge to its surroundings and becomes neutral once again.

What does the strength of the force depend on?

The distance

When the charges are closer together, what happens to the force?

The force becomes stronger

A rubber rod can be charged negatively when it is rubbed with wool. What happens to the charge of the wool? Why?

The wool becomes positively charged because it gives up electrons to the rubber rod

Why do socks taken from a clothes dryer sometimes cling to other clothes?

They have been charged by contact as they rub against other clothes, and thus, are attracted to clothing that is neutral or has an opposite charge

What happens to charges when objects get charged?

When objects get charged, their charges are separated

Is one Coulomb a lot of charge?

Yes, a Coulomb is a lot of charge

Can charged objects attract neutral objects

Yes, charged objects can attract neutral objects

conductor

a material through which a charge will move easily

insulator

a material through which a charge will not move easily

Neutral

an object whose positive charges are exactly balanced by its negative charges

A neutral metal sphere is touched by a positively charged metal rod. During the process, protons are transferred from the _____ to the _____ and the sphere acquires a _____ charge. a. charged rod, neutral sphere, negative b. charged rod, neutral sphere, positive c. neutral sphere, charged rod, negative d. neutral sphere, charged rod, positive e. ... nonsense! None of these describe what occurs.

e. ... nonsense! None of these describe what occurs.

True or False: charges can be created or destroyed

false--they are never created or destroyed

What is the quantity of charge related to?

force

If you comb your hair on a dry day, the comb can become positively charged. Can your

hair remain neutral? Explain. No. By conservation of charge, your hair must become negatively charged.

What do electrons contain?

low-mass, negatively charged particles

What does the atom contain?

massive, positively charged nucleus surrounded by a cloud of orbiting electrons

What is the charge of an atom?

neutral

What is the symbol for charge?

q

in the formula F=KQ(a)Q(b)/r^2 which has a greater affect on the force, A. Q(a) B. Q(b) C. R^2

r^2

Coulomb's Law

states the force between 2 point charges varies directly with the product o their charge and inversely with the square of the distance between them

charging by conduction

the process of charging a neutral object by touching it with a charged object

The closer the distance...

the stronger the force

Why are test particles always small and positive?

the test object is always small and positive so it doesn't affect what your testing

True or False: all objects contain charge

true

True or False: electrostatic force is a vector quantity

true

True or False: magnitude of force varies inversely with the square of the distance between the centers of the spheres

true

True or False: the charge affects the force

true

True or False: the force varies directly with the charge of the bodies

true

Where do electric charges exist?

within atoms