Physics Ch. 17
An object that is positively charged must have _________ electrons compared to its protons.
less
Each electron bears a net ___________ charge equal in magnitude but opposite in sign to a proton.
negative
The elementary unit of charge, the charge on an electron or proton is ______________.
1.60 x 10^-19 C
A neutral atom could be composed of
5 electrons, 5 protons, 6 neutrons
When the balloon is held near to the pop can (and before being touched by the hand), the distribution of charge on the pop can is best depicted by diagram ____________.
A (GET PHOTO)
When the balloon is held near to the pop can (and before being touched by the hand), the distribution of charge on the pop can is best depicted by diagram _______.
B (GET IMAGE)
T or f: Conductors cannot be charged by frictional rubbing.
False. Conductors can be charged by friction, however, you must handle the conductor with insulating gloves or similar materials in order to prevent the charge that it acquires from instantly grounding.
A physics teacher charges a balloon negatively by rubbing it with animal fur. The balloon is then placed next to a wooden cabinet and adheres to the cabinet. Explain what is happening at the particle level to cause such a gravity-defying phenomenon. Add to the blown-up view of the diagram to assist in your explanation.
The wood molecules polarize in such a manner that the positive poles of the molecules are closer to the balloon and the negative poles are furthest away. This causes a net attraction between the wood and the balloon.
T or f: When two objects made of different materials are rubbed together, the total amount of charge the two objects remains unchanged.
True
T or f: When two objects made of different materials are rubbed together, they each acquire a charge.
True
T or f: When two objects made of different materials are rubbed together, they will attract each other after the charging process.
True
Semi-conductor
a material with a conductive capacity between conductors and insulators
The diagram at the right shows a metal sphere attached to the top of an insulating stand. The metal sphere contains an excess of electrons and is thus charged. A student holds various objects in her hand and touches the object to the sphere. Which of the following objects below would allow charge to throw it when the student touches the object to the sphere?
a steel house key a strip of aluminum foil a metal paper clip
Describe the steps of conduction.
a) Teacher holds a negatively charged metal bar by its insulating handle and touches it to a metal sphere (attached to an insulating stand.) b) Teacher pulls the metal bar away and the metal sphere acquires a charge. c) The excess negative charge spreads uniformly about the surface of the metal sphere.
Describe the steps of conduction with a positively charged metal bar.
a) Teacher holds a positively charged metal bar by its insulating handle and touches it to a metal sphere (attached to an insulating stand.) b) The teacher pulls the metal bar away and the metal sphere acquires a charge. c) The excess positive charge is spread uniformly about the surface of the metal sphere.
Describe the process of charging by induction.
a) Uncharged metal pop can is attached to a Styrofoam cup (insulating stand) b) A negatively charged balloon is brought near the pop can. c) While the balloon is held near, the can is touched. d) When the can is pulled away, the pop can is charged.
Describe the steps of induction with a positively charged balloon.
a) Uncharged metal prop can is attached to a Styrofoam cup (which acts as an insulating stand.) b) A positively charged balloon is brought near the pop can. While the balloon is held near, the can is touched. c) When the can is pulled away the pop can is positively charged.
How do you do grounding?
a) neutral sphere on insulating stand b) touch with negative rod (becomes negative) c) touch (taking electrons) d) result is it is NEUTRAL
How do you do induction?
a) uncharged object on insulting stand b) touch neutral object with negative balloon c) touch neutral object with hand (taking away elec) d) result is a POSITIVE charge
A charged body of either sign will _______ a neutral body in which a charge separation is induced.
attract
The process of charging a neutral body by touching it with a charged body is called charging by ______________.
conduction
Charges added to a _______ will immediately spread throughout the body.
conductor
Because they are poor ________, rubber and glass rods are used for electrostatic experiments.
conductors
Materials through which electrons can move readily are classified as ________________.
conductors
The _____________ unit of charge is the quantity of charge on an electron or proton.
coulomb
The quantity of charge on an object is measured using a unit called the _____________.
coulomb
Insulators are no different than conductors in that insulators ____________.
do not allow charge to freely move
All electronic phenomena are due to the movements of _________.
electrons
The __________ are negatively charged.
electrons
In the charging of a solid, charge transfer is accomplished by the displacement of __________.
electrons only
When the pop can is touched by the hand, ___________ move from the ___________ to the _______________.
electrons, can, hand
When the pop can is touched by the hand, ________move from the __________ to the ____________.
electrons, hand, can
When the positively charged sphere is touched ____________ move from the ____________ to the _______________.
electrons, hand, sphere
The charged parts of the atom are the ____________ and the ___________.
electrons, protons
When the negatively charged sphere is touched, ______________move from the ________________ to the _______________.
electrons, sphere, hand
An __________ is a device used to detect the presence of a static charge.
electroscope
A balloon is charged by rubbing it with animal fur. It is then pressed against a wooden cabinet. The balloon and cabinet attract, seeming to defy the force of gravity. This attraction is best explained by ____________.
frictional charging of the wood
When you rub a glass rod with a silk cloth, electrons are transferred from the _________ to the ________. As a result, the glass rod acquires a ________ charge and the silk cloth acquires a _______ charge.
glass, silk, positive, negative
negatively charged
greater e than p
positively charged
greater p than e
The process of neutralizing the charged spheres as depicted above is know as _______________.
grounding
An electrically neutral atom is an atom which __________________.
has a balance of protons and electrons (the same number of each)
An electrically charged atom (sometimes referred to as an ion) can be distinguished from an electrically neutral atom n that the charged atom (ion) _______________.
has an imbalance of protons and electrons (unequal numbers of these)
If a positively charged rod touches a neutral metal plate, the number of electrons on the rod will __________.
increase
Charges added to one part of a ________ will remain in that part.
insulator
The above effect (frictional charging of wood) is most often noticed of ____________.
insulators
Insulator
keeps current in one area
Then Miss Chiff touches her students. As she does, some electrons leave Miss Chiff and move onto her students. Miss Chiff is now ________ than before the contact with the student. And the student is now charged with a ______ type of charge.
less, negative
An object that is negatively charged must have __________ electrons compared to its protons.
more
Explain what must happen in order for an oxygen atom to become negatively charged.
must accept nearby electrons
Explain what must happen in order for an oxygen atom to become positively charged.
must lose its own electrons
Miss Chiff stands at the door of her classroom, scuffing her feet back and forth on the carpet. As she does so, electrons move from the carpet to her shoes to her body. Miss Chiff is now charged with a _______ type of charge.
negative
This process causes the can to acquire a ___________ charge.
negative
The object that gains the electrons acquires a _______________ charge and the object that loses the electrons acquires a __________ charge.
negative, positive
Suppose you rub a glass rod with a silk cloth and a second glass rod with rabbit fur. The silk cloth will acquire a ______ charge; the rabbit fur will acquire a _________ charge. The rabbit fur and the silk cloth will then be observed to ________ each other.
negative, positive, attract
Under ordinary circumstances, an atom is electronically ________.
neutral
The ____________are not charged and thus will not be of importance in this unit.
neutrons
The standard metric units of measurements for electric field strength are ________________.
newton/coulomb
Conductor
object that allows flow of current in one or more directions
The process of inducing the movement of charge within the sphere causes positive and negative charge to be separated. This is known as ________________.
polarization
In the above situation, the conducting sphere is ____________. List all that apply.
polarized
In general, the use of a negatively charged object to charge another object by induction causes the other object to acquire a _________ charge.
positive
This process (induction) causes the can to acquire a ____________ charge.
positive
Object A is rubbed with object B. Object C is rubbed with object D. Objects A and D are observed to repel each other. Object B is observed to repel a negatively charged balloon. This is conclusive evidence that _________. Object A acquired a _________ charge. Object B acquired a _________ charge. Object C acquired a _________ charge. Object D acquired a __________ charge.
positive, negative, negative, positive
Suppose you rub a rubber rod with a silk cloth and a second rubber rod with a wool sweater. The silk cloth will acquire ___________ charge; the wool sweater will acquire a __________ charge. The sweater and the cloth will then be observed to ________ each other.
positive, positive, repel
A neutral object becomes _________ charged if electrons are removed.
positively
Induction
process of charging positively (see steps)
The __________ are positively charged.
protons
The _______________ reside in the nucleus of atoms and are tightly bound, they will never leave an atom as a result of electrostatic procedures.
protons
In a lab report during the Static Electricity unit, Aaron Agin suggests that a sample of wool became positively charged by gaining protons from the rubber balloon that it rubbed. Explain what is wrong with Aaron's statement.
protons never move, only electrons move
When you pull a cotton sweater off your skin, electrons are transferred from the _______________ to the _____________. As a result, your body acquires a ________________ charge and the cotton sweater acquires a __________ charge.
skin, cotton, positive, negative
When the metal bar is pulled away in Diagram B, the metal bar is _________________.
still negatively charged, but has fewer excess electrons than it previously did.
When the metal bar is pulled away in Diagram B the metal bar is ________.
still negatively charged, but has fewer excess protons than it previously did.
When the induction process is complete, the balloon is ____________.
still negatively charged, having the same amount of negative charge as it previously had
The direction of this electric field vector is defined as ______________________________________________.
the direction that a positive test charge would be pushed or pulled if placed at the given location.
This process (charging and then touching the can with a hand) is known as __________.
Charging by induction.
Charged rubber rods are placed near a neutral conducting sphere, causing a redistribution of charge on the spheres. Which of the diagrams below depict the proper distribution of the spheres? List all that apply.
GET IMAGE
electrically neutral
same e and p
An object that is electrically neutral must have ________ electrons compared to its protons.
same number of
_________________ are materials with a conductive capacity between conductors and insulators.
semiconductors
If two spheres were touched together and separated (net charge (-6), the charge on sphere A would be ___________.
-3
A meal sphere A has a charge of -2 units and identical sphere B has a charge of -4 units. If the two spheres are brought together and then separated, the charge on sphere A will be _______.
-3 units
If the two original spheres (three charges each) are moved twice as far apart, the force between them will change by a factor of __________.
1/4
__________ first stated the law relating electrical forces to charge and distance.
Coulomb
A negatively charged balloon is brought near a neutral conducting sphere as shown in the diagram at the right. The presence of the charged balloon will cause something to happen in the sphere. Which of the following would you expect to occur? Select all that apply.
Electrons in the sphere will move to the right side
Diagram A is the charging step. How does the sphere become charged?
Electrons move from the charged metal bar into the sphere.
Diagram A is the charging step. How does the sphere become charged?
Electrons move from the sphere into the positively charged bar.
T or f: When two objects made of different materials are rubbed together, one object gains electrons and the other objects gains protons.
False
T or f: When two objects made of different materials are rubbed together, they will either be both charged positively or both charged negatively.
False
Consider these two spheres. They both have been charged. In one case the charge is isolated in three distinct locations; in the other case, the excess charge is even distributed about the surface of the sphere. Which one of these spheres is made of an insulating material and which is made of a conducting material? Label which is which and support your answer with an explanation.
Insulating localizes the charge, conducting distributes it
Which of the following diagrams shown below best represents the electric field around the two spheres?
One (GET PHOTO)
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? Explain.
Saran Wrap. It takes electrons.
A 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.
The felt became charged negatively during this rubbing process. If the glass acquired a charge of +5 units, then the felt acquires a charge of -5 units Once charged in this manner, the glass object and the felt cloth should attract each other.
Diagram C shows the excess negative charge distributed differently than it is in Diagram B. Explain why the excess negative charge would distribute itself as it does in Diagram C.
The metal sphere is a conductor that allows electrons to flow freely. The excess electrons repel one another and spread uniformly across the surface of the metal sphere.
Explain what happens if you bring a charged object near a neutral object. Ex: balloon to board.
The negative charges in the board are repelled. This leaves a positive charge on the board, the balloon sticks, over time electrons transfer and it falls
A physics teacher fills a buret with water and opens the valve, producing a steady stream of water falling vertically to the sink. Then the teacher rubs a rubber balloon with animal fur and holds it near the stream. The stream is observed to deflect from its usual vertical flow towards the balloon. Explain what is causing the deflection of the water stream.
The negatively charged balloon induces the water molecules to become polarized. The molecules flip around and orient themselves such that the more positive H atoms are furthest away. There is thus a net attraction of the balloon for the water stream, deflecting the stream from its otherwise vertical flow.
A metal sphere is resting upon an insulating stand. A teacher holds a metal bar (with an insulating handle.) The teacher uses the metal bar to charge the metal sphere by conduction. Which one of the processes describes what the teacher likely did to charge the sphere by conduction?
The teacher charged the bar and then contacted it t the sphere.
An electron enters the space between two oppositely charged parallel plates as shown in the diagram. What is the direction of the electrical force on the electron as it passes between the plates?
Toward the positive plate
Unlike charges ______________ one another.
attract
If one charge is removed from one of the spheres and placed on the other sphere, the electric force between the spheres will ____________.
decrease
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 ___________________.
the plastic strip lost electrons to the cotton during the charging process
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 _____________________.
the plastic strip lost electrons to the cotton during the charging process
Coulomb
unit of charge indicating quantity of charge on electron or proton
Balloons A and B are suspended from the ceiling by light threads; each balloon is made of rubber. Balloon A was rubbed with animal fur. Balloon B was rubbed with animal fur. If a negatively charged plastic tube were inserted between the two balloons, then one would observe that the two balloons ______________.
would deflect even more from a vertical orientation
