Ch. 20 Flashcards
how are charges and electric fields related
charges create an electric field
when is an object neutral
when it has equal amounts of positive and negative charges
when does an object become negatively charged
when the amount of negative charge on it exceeds the amount of positive charge
when does an object become positively charged
when it has more positive charge than negative charge
what type of force is the force between two particles
they are action-reaction pair that are equal in magnitude and opposite in direction
if you increase the distance between two objects what happens?
the force decreases (inversely proportional to the square of the distance)
if you decrease the charge on two objects what happens to the force between them
it decreases
what do we use coulomb’s law for
we use it to calculate the force between two charged objects
what is charge an inherent property of?
electrons and protons
a neutral macroscopic object has how many protons and electrons
the same
how are protons and electrons similar
they have the same exact (opposite) charge despite the electron being less massive
how do objects gain a positive charge
by losing electrons (valency)
what is ionization
it is the process of removing an electron from the electron cloud of an atom to produce a positive ion
what is an insulator
electrons are tightly bound to the positive nuclei within and are not free to move around, electric charge cannot pass through
what is a conductor
In metals, the outer electrons (valence) are weakly bound and can detach from their parent ion and can move through the solid
what is an electric dipole
an electric dipole is equal but opposite charges with a separation between them
what is the field model
it explains how the force due to charges is transmitted through empty space
when Charge B experiences a force from charge A, what is actually the agent?
the alteration of space around a charge is the agent that exerts a force on charge B
which way does an electric force point on a positive charge?
it points away from it. . For example, if a positive source charge generates an electric field that points away from it, then a positive test charge placed in the field will feel a force in the same direction, away from the source charge.
which way does an electric field force vector point on a negative charge
it points towards it, a positive charge placed in the electric field of a negative charge would feel a force vector towards the negative charge
how do you draw an electric field vector?
you draw it tangent to the electric field line
where is an electric field stronger?
it is stronger where the electric field vectors are longer and closer together
the electric field at any point is the
vector addition of the individual fields
what are the rules for drawing electric field lines
draw the field lines starting on the positive charges and moving toward the negative charges
make the lines close together where the field is stronger
what is true of the electric field in a parallel plate capacitor
the electric field at every point is the same in strength and direction (this is the uniform electric field)
what does the electric field in a parallel play capacitor depend on?
It depends on the charge and area of the plates
what does it mean when a conductor is in electrostatic equilibrium
no charges are moving
when a conductor is in electrostatic equilibirum, what is true about the electric field?
it is zero
what happens to the excess charge in a conductor at estatic equilibrium?
the charge moves to the surface and the electric field is perpendicular to the surface
where is the electric field stronger in a conductor?
at sharp points the density of the charge is higher
If you place a charged object next to an uncharged object that is a conductor,
There is an attractive force between the two objects.
A negatively charged rod is brought near a neutral metal sphere. Which of the following is true?
There is an attractive force between the rod and sphere.
A neutral object __________.
has no net charge
According to Coulomb’s law, when the distance between two point charges doubles, what happens to the electric force acting between the charges?
It goes down by a factor of 4.
Electric fields exist ____________.
at all points in space around charges
The clothes are charged by ______
in the drier. Your body is neutral but the clothes can ______
you a little and attract the opposite charge in your body.
rubbing; polarize
is glass and plastic a conductor or insulator
it is a insulator
is metal a conductor or insulator
it is a conductor
can insulators and conductors be charged?
yes they can be charged but they differ in their abiltiies to move
is the force between a charged object and a neutral object attractive or repulsive?
it is attractive due to polarization
if an object is charged, what is true about the electrons and protons
there is a difference between them
if you rub silk, saran wrap, or polyester on glass, what happens to the charge on the glass?
glass tends to lose electrons so it becomes positive while the silk, wrap, or polyester gains those electrons
if you rub a PVC or rubber rod on wool, hair, or nylon, what happens to the charge on the rod?
PVC tends to gain electrons so it will become negative while the other materials become positive
what is grounding
it is the ability to absorb positive or negative charges
what direction does the electric force on a negative charge point if the electric field is down?
if the electric field is down, the force acting on the charge is opposite so it is pointing up
