physics chapter 16-17A
Doubling the distance from a point charge would cause the electric field to become a. one-fourth as great b. one-half as great c. twice as great d. four times as great
a
The magnitude of the electric field 5 m from a 2 nC charge is a. 0.72 N/C b. 3.6 N/C c. 360 N/C d. 720 N/C
a
The transfer of charge from one object to another through direct physical contact is called a. Conduction b. Induction c. Polarization d. Quantization
a
Which of the following is NOT a property of electric field lines? a. The field is perpendicular to the field lines at each point. b. The number of lines per unit area is related to the strength of the field. c. They point away from positive charge and toward negative. d. Field lines never cross.
a
capacitor
a device that stores electric charge and energy in a way that can be reclaimed later when needed for a specific application
electric current
a flow of electric charge
van de graaff generator
a machine designed to generate a large buildup of electric charge
capacitance
a measure of the amount of electric charge stored (or separated) for a given potential difference
electric charge
a property of a particle by which it may repel or attract other particles
Charges on the dielectric _____ with the electric field created by the charged capacitor plates
align
dielectric
an insulating material used to fill the space between the plates of a capacitor (air rubber glass)
the electrostatic force can be either ________ or _________
attractive; repulsive
A material that DOES NOT transfer charge easily is called a a. Conductor b. Insulator c. Semiconductor d. Superconductor
b
The amount of charge stored on 25 pF capacitor when connected across a 9 V potential difference is a. 1.01 x 10-9 C b. 2.25 x 10-10 C c. 4.5 x 10-10 C d. 2.78 x 10-12 C
b
The potential difference between a point located 5 m from a 2 microcoulomb charge and a second point at infinity is a. 720 V b. 3600 V c. 11,250 V d. 22,500 V
b
The type of charging in which a positive rod is used to lure electrons onto an object through grounding is called a. conduction b. induction c. polarization d. quantization
b
The work done when moving a 5 C charge through a potential difference of 100 V is a. 20 J b. 500 J c. 2,500 J d. 50,000 J
b
Which of the following DOES NOT correctly describe electric charge? a. Objects are electrically charged through rubbing b. Like charges attract and opposites repel c. The charge on any object is always a multiple of the elementary charge d. Electric charge is conserved
b
process of induction (4)
1. bringing a positively charged rubber rod near an electroscope causes the charges on the electroscope to redistribute (since opposites attract, likes repel) 2. grounding the electroscope allows electrons to enter it from the earth 3. a net negative charge is left behind 4. the net negative charge redistributes itself throughout the electroscope once the rod is removed (produces the OPPOSITE CHARGE)
ways you can transfer electric charge (3)
1. conduction 2. induction 3. polarization
process of polarization (3)
1. in neutral atoms and molecules, the centers of positive and negative charge typically coincide 2. bringing a positively charged object near an insulator causes its centers of positive and negative charge to shift slightly, bringing the negative center closer to the surface (due to the attraction with the positive object) and the positive center farther from the surface (due to repulsion) 3. the resultant effect is a realignment of charge on the surface of the insulator, leaving it with no net charge, but with an ability to attract or repel other objects
properties of electric charge (4)
1. objects are electrically charged through rubbing 2. two kinds of charge exist- positive and negative 3. like charges repel, opposites attract 4. electric charge is "quantized"-the charge on any object is always a multiple of the charge of a single proton or electron
structure of an atom (3)
1. positively charged particles called protons (in the nucleus) 2. negatively charged particles called electrons (in shells surrounding the nucleus) 3. neutrally charged particles called neutrons (in the nucleus)
when an isolated conductor is in electrostatic equilibrium (4)
1. the electric field is zero everywhere else inside the conductor 2. any excess charge resides entirely on the surface of the conductor 3. the electric field just outside a charged conductor is perpendicular to its surface 4. while excess charge always spreads out evenly over the surface of a spherical conductor, charges tend to accumulate at sharp points on non spherical conductors
electric field line conventions: (4)
1. the field is always tangent to the field lines at each point 2. the number of lines per unit area is proportional to the strength of the electric field (close lines=strong field) 3. field line point always stay away from positive charge and towards negative charge 4. electric field lines never cross (they are 3D)
process of conduction (3)
1. touching a positively charged rubber rod to the top of an electroscope allows some of the electrons to leave the electroscope and travel down the rod (since opposites attract) 2. a net positive charge is left behind 3. the net positive charge redistributes itself throughout the electroscope once the rod is removed
Which of the following is NOT a property of a conductor in electrostatic equilibrium? a. the electric field is zero everywhere inside the conductor. b. any excess charge resides inside the conductor. c. The electric field just outside the conductor is perpendicular to its surface. d. On non-spherical conductors, charge tends to accumulate at sharp corners.
b
superconductors (definition and examples)
become perfect conductors when at or below a certain temperature (lose NO energy); tin below 4 K
The capacitance of a parallel-plate capacitor with two plates of area 2 m2 separated by 0.25 m is a. 1.42 x 10-10 F b. 2.83 x 10-10 F c. 7.08 x 10-11 F d. 1.11 x 10-12 F
c
The electric force between two 3 C charges separated by 2 m is a. 4.00 x 109 N b. 6.75 x 109 N c. 2.03 x 1010 N d. 4.05 x 1010 N
c
The potential difference when a 2 C charge is moved 5 m in the direction of a 10 N/C uniform electric field is a. -2 V b. 2 V c. -50 V d. 50 V
c
The type of charging in which a neutral object has its positive and negative centers of charge realigned is called a. conduction b. induction c. polarization d. quantization
c
Which of the following DOES NOT correctly describe a dielectric material? a. A dielectric is a insulating material. b. Air, rubber, and glass are common dielectric materials. c. Adding a dielectric to a capacitor decreases its capacitance. d. Applying high voltages across a capacitor can destroy a dielectric.
c
Which of the following DOES NOT correctly describe a fully-charged capacitor? a. One plate is positive and the other is negative. b. The net charges on the two plates are equal in magnitude. c. The net charges on the two plates have the same sign. d. The voltage across the plates is the same as that of the battery.
c
Which particles are most easily transferred from one object to another? a. protons b. neutrons c. electrons d. ions
c
induction only works with _______
conductors
electric charge is _________
conserved (charge can be transferred but cannot be created or destroyed)
A particle with two unbalanced electrons has a net charge of a. 1.6 x 10-19 C b. -1.6 x 10-19 C c. 3.2 x 10-19 C d. -3.2 x 10-19 C
d
The electric potential energy that is stored in a 50 pF capacitor when connected to a 6 V potential dfference is a. 1.8 x 10-9 J b. 1.5 x 10-10 J c. 3 x 10-10 J d. 9 x 10-10 J
d
The magnitude of the force that would act on a 5 C charge placed in a 1000 N/C electric field is a. 0.005 N b. 200 N c. 500 N d. 5000 N
d
insulator (definition and examples)
do not transfer charge easily; glass, rubber, plastic
a charge has _______ potential energy as a result of its location in an electric field
electrical
an object with no net charge has an ________ number of protons and electrons
equal
a charge that experiences no net electrostatic force is said to be in ____________
equilibrium
millikans experiment
examined the motion of tiny oil drops between a pair of parallel metal plates as means of determining the charge of an electron
true or false: The purpose of Millikan's Experiment was to determine the mass of the electron.
false
true or false: polarization involves physical contact between objects
false
the electrostatic force is a ______ force, and thus has the ability to act between charged objects that are not in direct contact
field
the strength of the electric field at any particular location can be found by placing small positive "test charge" qo at that location, measuring the force F acting on it, and then calculating the _______ per unit _______ being exerted (E=F/qo)
force; charge (measured in N/C)
principle of superposition
if more than two charges are present, the net electrostatic force on any one of them is given by the vector sum of the forces exerted on that charge by all of the other charges that are present
a dialectic __________ capacitance by allowing the capacitor plates to store more charge with the same applied potential difference
increases
polarization is similar to induction, but only works with ___________
insulators
atoms that are positively or negatively charged are called ____
ions
electric field lines
lines that represent and help us to visualize both the magnitude and direction of the electric field surrounding one or more charges
more charge means...
more potential energy
a neutral object that gains an electron takes on a net ______ charge
negative
conduction involves actual charge transfer from one object to another through ________ contact
physical
a neutral object that loses an electron takes on a net _______ charge
positive
E is a vector and always points away from ________ charge and towards ______ charge
positive; negative
semiconductor (definition and examples)
properties somewhere between that of a conductor and an insulator; silicon, germanium
when charging by conduction, you are charging by the ____ charge as the original object
same
the amount of charge of protons and electrons is the ____, protons, though, are _______, and electrons are ______
same; positive; negative
electric charge is the result of the ________ of an atom
structure
potential difference
the change in electric potential energy per unit charge between two points in an electric field
electrostatic equilibrium
the condition in which there is no net motion of charge within a conductor
electric potential
the electric potential per unit charge at any location in an electric field
coulomb's law
the magnitude of electrostatic forces that any two charges exert on another is given by F=kq1q2/r^2
electric field
the region in space surrounding a charged object in which a stationary charge experiences an electrostatic force
electrostatics
the study of electric charges at rest
conductor (definition and examples)
transfer charge easily; copper, aluminum, gold
true or false: A Van de Graaff Generator is a machine designed to generate a large build-up of electric charge.
true
true or false: Electric potential energy depends on the size of the charge placed at a particular location while electric potential does not.
true
true or false: conduction works with both conductors and insulators
true
true or false: in a good conductor, charges are free to move about within the material
true
true or false: induction involves no physical contact between objects
true
how is a corona produced
when a large number of charges accumulate on the surface of a conductor, the strong repulsive forces between them sometimes cause one or more of them to jump to the surrounding air, creating the corona
Energy is stored in a capacitor during the charging process as a result of the _____ done to move the charges from one plate to another
work
________ is done by electric forces whenever a charge is moved through a potential difference
work
