Physics Chapter 22 Electricity and Magnetism: Terms, Practice Homework, Practice Test
Two charges separated by one meter exert 1-N forces on each other. If the charges are pulled 3 meters apart, the force on each charge will be
0.11N
Two charges that are separated by one meter exert 1-N forces on each other. If the magnitude of each charge is doubled, the force on each charge is
4N
How does one coulomb of charge compare with the charge of a single electron
A coulomb of charge is the charge associated with 6.25 × 1018 electrons
Why is there no electric field at the center of a charged spherical metal ball
Because of mutual repulsion, mobile electrons in the conductor will spread out uniformly over the outer surface of the ball, so the force and the field on a test charge at the center is zero because opposing forces balance in every direction
Electric Field Equation Form
Electric Field= F/q
Electric Potential Equation Form
Electric Potential=Electric potential energy/amount of charge
The fundamental force underlying all chemical reactions is
Electrical
Why are materials such as glass and rubber good insulators
Electrons are tightly bound to their atoms, making them poor conductors of heat.
What happens to electrons in any charging process
Electrons transfer from one place to another
What term is used for "electricity at rest"
Electrostatic
What term is used for electricity at rest
Electrostatics
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
F/2
Where is the energy stored in a capacitor
The energy is stored in the electric field between the plates
Why does the gravitational force between Earth and Moon predominate over electrical forces
The electric force between Earth and Moon cancels out because they have an equal number of positive and negative charges
Protons
are about 1800 times more massive than electrons, but each one carries an amount of positive charge equal to the negative charge of electrons
An electron and a proton
attract each other
Electric charge can be transferred from one conducting body to another
by both contact and closeness
It is said that electric charge is conserved, which means that electric charge
can be neither created nor destroyed
Atoms
have as many electrons as protons, so the atom has zero net charge
Neutrons
have slightly more mass than protons and have not net charge
It is said that electric charge is quantized, which means that the charge on an object
is a whole-number multiple of the charge of one electron
To become a positive ion, an atom must
lose an electron
To say that electric charge is conserved means that no case has ever been found where
net charge has been created or destroyed
When a charged comb is brought nearby, molecules in the paper are
polarized
A positive ion has more
protons than electrons
When the distance between two charges is halved, the electrical force between them
quadruples
A main difference between gravitational and electric forces is that electrical forces
repel or attract
Two charged particles held a certain distance apart are released. As they move, the acceleration of each decreases. Therefore, their charges have
the same sign
When we say charge is conserved, we mainly mean that charge can be
transferred without loss like money in a bank
Electric potential, unlike electric potential energy, is measured in units of
volts
Most atoms normally have a net charge that is
zero
The net charge on a polarized molecule is normally
zero
To become a negative ion, an atom must
gain an electron
When you brush your hair and scrape electrons from your hair, the charge of your hair is
Positive Charge
If electrons are stripped from an atom it becomes a
Positive Ion
The electrical force between charges is strongest when the charges are
Close together
Capacitor
1. An Electrical Device 2. A pair of parallel conducting plates separated by a small distance 3. Stores Electric Charge and Energy 4.When the plates are connected to a charging device, such as the battery, electrons are transferred from one plate to the other.
Electric Field
1. An Electrical Force per unit of charge. 2. Space surrounding an Electric Charge, Which is a storehouse of Electric Energy 3.The field decreases (directly) with inverse square law 4. They are parallel plates 5. They are Uniform
The electrical force between electric charges depends only on their
1. Magnitude 2. separation Distance
Electric Force and Charges: Ion
1. Positive Ion 2.Negative Ion
How much energy is given to each coulomb of charge that flows through a 1.5-V battery
1.5 joules
What are four areas that are involved with the study of Electrostatics
1.Electric Charges 2.The forces between them 3.The aura that surround them 4.Their behavior in materials
Differences between gravitational and electrical forces
1.Electrical forces may be either attractive or repulsive. 2.Gravitational forces are only attractive
Electric Potential Energy
1.Energy possessed by a charged particle due to its location in an Electric Field. 2.Work is required to push a charged particle against the electric field of a charged body 3.Called Voltage-Potential Energy per Charge
Electric Force and Charges: Fundamental Facts about Atoms
1.Every atom is composed of a positively charged nucleus surrounded by negatively charged electrons 2.Each of the electrons in any atom has the same quantity of negative charge and the same mass.
Electric Potential: Voltage
1.High voltage can occur at low electric potential energy for a small amount of charge. 2.High voltage at high electric potential energy occurs for lots of charge
Electric Force and Charges: Electrons in an Atom
1.Innermost 2.Outermost
Electric Force and Charges: Electrons
1.Negative Electric Charges 2.Repel Negatives, but attract positives
Electric Force and Charges: Neutrons
1.Neutral Electric Charge
Electric Force and Charges: Protons
1.Positive Electric Charges 2.Repel Positives, but attract negatives
Electric Field Direction
1.Same direction as the force on a positive charge 2.Opposite direction to the force on an electron
Semiconductors
A material with properties that fall in the middle range of electrical resistivity between insulators and conductors -They are insulators when they are in their pure state. -They are conductors when they have impurities
What is a positive ion? What is a negative ion?
A positive ion is a neutral atom that has lost one or more electrons. A negative ion is a neutral atom that has gained one or more Electrons
What is a positive ion? What is a negative ion?
A positive ion is a neutral atom that has lost one or more electrons. A negative ion is a neutral atom that has gained one or more electrons.
What is meant by saying that charge is quantized
All charged objects have a charge that is an integer multiple of the charge of an electron.
How does the charge of one electron compare to that of another electron? How does it compare with the charge of a proton? How do the masses of protons and electrons compare
All electrons have the same charge. Electron charge is equal and opposite to the proton charge. A proton has 1800 times the mass of an electron
In terms of net charge, how does an electrically polarized object differ from an electrically charged object
An electrically polarized object can have zero net charge, while a charged object cannot have zero net charge
When you buy a water pipe in a hardware store, the water isn't included. When you buy copper wire, electrons
Are already in the wire
Electric Force and Charges: Negative Ion
Atom Gaining one or more Electrons has negative net charge
Electric Force and Charges: Positive Ion
Atom Losing one or more Electrons have positive net charge
Coulomb's Law: Charge Polarization
Atom or molecule in which the charges are aligned with a slight excess of positive charge on one side and slight excess of negative charge on the other are called Electrically Polarized
Electrons in an Atom: Outermost
Attracted loosely and con be easily dislodged
Electrons in an Atom: Innermost
Attracted very strongly to oppositely charged Atomic Nucleus
Rub an inflated balloon on your hair and place the balloon on the wall. The balloon sticks to the wall due to charge polarization in the atoms or molecules of the wall
Charge polarization
Give two examples of common force fields and name the sources of these fields
Gravity fields made by mass, electric fields made by charge
Semiconductors conduct when light shines on it
If a charged selenium plate is exposed to a pattern of light; the charge will leak away only from the areas exposed to light.
Charge Polarization
If the charged rod is negative then the positive part of the atom or molecule is tugged in a direction toward the rod, and the negative side of the atom or molecule is pushed in a direction away from the rod -The positive and negative parts of the atoms and molecules become aligned. They are Electrically Polarized
Electric potential energy is measured in joules. Electric potential, on the other hand (electric potential energy per charge), is measured
In Volts
What is an electric dipole
In an electric dipole, positive and negative charges are separated on opposite sides of an object
Conservation of Charge
In any charging process No Electrons are Created or Destroyed. Electrons are simply transferred from one material to another. The total charge before an interaction equals to total charge after
Electrostatic
Involves Electric Charges, the forces between them, the aura that surround them, and their behavior in materials
An electrically charged atom is an
Ion
Insulators
Materials in which electrons are Tightly Bound and belong to particular atoms in the material, which charge does not easily flow Example: Rubber, and Glass
Conductor
Materials in which one or more of the electrons in the outer shell of its atoms are not anchored to the nuclei of particular atoms but are Free to Wander in the material. Example: Metals such as copper and aluminum
Superconductors
Materials that is a perfect conductor with zero resistance to the flow of electric charge -Once electric current is established in a superconductor, the electrons flow indefinitely -With no electrical resistance, current passes through a superconductor without losing energy -No heat loss occurs when charges flow
Electricity
Name given to a wide range of Electrical Phenomena, such as lighting, spark when we strike a match and what holds atoms together.
If electrons were scraped off the brush onto your hair, your hair would have
Negative Charge
Rub electrons from your hair with a comb and the comb becomes
Negatively Charged
What is meant by conservation of charge
Net charge cannot be created or destroyed
What is the most common net charge of an atom
Neutral
Which of these does NOT have an electrical charge
Neutrons
How is Coulomb's law similar to Newton's law of gravitation? How is it different
Newton's law of gravitation is attractive, whereas Coulomb's law is attractive or repulsive. Both are proportional to the inverse square of distance.
Coulomb's law is most similar to which of these laws
Newton's law of gravity
Protons and Neutrons are compose of
Nucleus
According to Coulomb's law, a pair of particles that are placed twice as far apart will experience forces that are
One-quarter as strong
Electric Force and Charges: Central Rule of Electricity
Opposite charges attract one another; like charges repel
Electrons transfer from one material to another by
Simply Touching - When a negatively charged rod is placed in contact with a neutral object, some electrons will move to the neutral object
How does the flow of current differ in a superconductor compared with the flow in ordinary conductors
Superconductors have infinite conductivity (current flows forever), whereas ordinary conductors have a small resistance to the flow of electric charge
Coulomb
The SI Unit of Electric Charge. One Coulomb (symbol C) is equal to the total charge of 6.25 * 10^18
What would happen to the two balls if both of them had a non-neutral charge and you slowly increased the mass of the balls?
The angle of the balls with respect to the vertical would decrease.
What would happen to the two balls if one of them were kept positively charged and the charge on the other ball were slowly made increasingly negative
The balls would begin to move closer together
What would happen to the two balls if one of them were kept positively charged and the charge on the other ball were slowly increased, making it more and more positive
The balls would begin to move closer together.
How is the direction of an electric field defined
The direction of the field is the direction of the force on a positive test charge
Which part of an atom is positively charged, and which part is negatively charged
The nucleus is positively charged and the electron cloud is negatively charged
Why are metals good conductors of both heat and electricity
The outer shell electrons in metals are free to move from atom to atom
Charging by induction
The redistribution of electric charges in and on objects caused by the electrical influence of a charged object close by but not in contact. Example: The Negative charge at the bottom of the cloud induces a positive charge on the buildings below
Coulomb's Law
The relationship among electrical force, charge and distance: 1.If the charges are alike in sign, the force is repulsive 2.If the charges are unlike, the force is attractive.
Charging by Friction and Contact
The transfer of electric charges between objects by rubbing or simple touching. Example: Stroking cats fur, combing your hair rubbing your shoes on a carpet
What is the primary purpose of a lightning rod
To prevent a fire caused by lightning
A fundamental rule of electricity is that
Unlike kinds of charges attract and like kinds of charges repel
The force that binds atoms together to form molecules is
electrical
Just as "gravity" is the study of a wide range of gravitational interactions, "electricity" is the study of a wide range of
electrical interactions
In an electrically neutral atom the number of protons in the nucleus is equal to the number of
electrons that surround the nucleus
The unit of electric charge, the coulomb, is the charge on a
specific large number of electrons
