Electric Charges & Electric Flux

Name the case for a spherical gaussian surface where the electrical field inside the surface becomes relevant?

When a spherical distribution occupies a volume

Planar symmetry

When charges are uniformly spread over a large flat surface

Can there be a non-zero electric field at a point in space where no charged object is present? Can there be an electric field equal to zero at a point where a charged object is present?

Yes to both. Therefore, the field can have any value (zero or non-zero) totally independent of what object is placed there.

Is it possible to create a charged object from an object that is neutral without transferring charge? If so, how?

Yes you can create a charged object through charging via induction

Where do excess charges outside the conductor always end up? a. on the surface of the conductor b. inside the conductor c. free space d. clustered around the conductor but not on the surface

a. on the surface of the conductor, no matter where they originate from

What does charging by induction create?

an electric dipole moment

In planar symmetry, all points in a plane parallel to the plane of charges are _________________ with respect to the other charges a. opposite to each other b. identical c. perpendicular to the surface

b. identical with respect to the charges

Electric field lines must be ___________

continuous

Electric field lines can never _________

cross

The electric field and the electric force are the same quantities (T/F)

false, the electric force produces an electric field, however the two are not one in the same

what is the range of the electric field?

infinite

If no charges are included within a closed surface what is the value of the electric flux?

it must be zero

the number of field lines is directly proportional to the ______________________

magnitude of the charge

Objects A and B are electrically repelled from each other. Can we tell what sign the charge of object A is?

no

what are the three types of symmetry for Gauss' Law?

spherical, cylindrical, and planar symmetry

What occurs when electrostatic equilibrium is reached?

the charge distributed in such a way that the electric field inside the conductor reaches 0

sphereical symmetry

the electric field at any point must be radially directed because the charge and the field must be invariant under rotation

Describe the electric field inside a conductor

the electric field inside a conductor is 0

how are electric field lines oriented when it is interacting with a conductor?

the electric field lines are perpendicular to the surface

Electric flux

the electric field passing through a given area

when electric field lines enter a closed surface what is the sign of the electric flux?

the electric flux is negative

when electric field lines leave a closed surface what is the sign of the electric flux?

the electric flux is positive

Field Line Density

the number of field lines per unit area passing through a small cross-sectional area perpendicular to the electric field

Electric field

the space around a charged object in which another charged object experiences an electric force

Gauss' Law

the total flux summed over any closed surface is equal to the net charge enclosed by the surface divided by the permittivity of free space.

In which direction do electric field lines travel with a positive source charge?

the travel outwards

According to Gauss' Law there is no net charge _____________?

there is no net charge within the conductor

what is the direction of the area vector and the electric field on a Gaussian surface?

they are parallel to each other

Electric field lines of similar charge face in which direction from each other?

they point away from each other since like charges repel each other

Electric field lines of opposite charge face in which way from each other?

they point towards each other, connecting

In which direction do negative electric field lines travel?

they travel inward toward the source charge

The direction of the electric field is the same direction of the electric force (T/F)

true

if there are point charges A,B, & C how would you determine the resultant force acting on charge A?

you would use the sum of vectors and use Coulomb's equation to find the electrical force acting on A at B & C then add them together

The electric force on object B by object A is F. If the distance between the objects were tripled, but everything else was kept the same, what would be the new electric force on object B by object A?

1/9F

The electric force on object A by object B is F. If the charge of object B were only half as large as it is, but everything else was kept the same, what would be the new electric force on object B by object A?

1/2F

Insulator

A material that does not allow or does a very poor job of conducting electricity

Conductor

A material that is capable of conducting electricity well

charging by induction

A process in which a neutral object becomes polarized after a positively/negatively charged rod is brought close to the neutral object making the oppositely charged particles venture close to the rod while the similar charged particles move away

Conduction electrons

Electrons in a metal that are free to move when an electric charge or field is applied

Neutral objects cannot be attracted to a charged object because they are neutral (T/F)

FALSE, a charged object has more protons/electrons than an object that is neutral which then creates an attractive force between the opposite particles in the neutral object and the charged object

Cylindrical symmetry

If the charge density depends only upon the distance from the axis of a cylinder and must not vary along the axis or with direction about the axis

What occurs if excess charge is added to an insulator?

Nothing will occur, the excess charge will remain in place on the material until it dissipates

how do you calculate the electric force exerted by object A on object A?

Object A will never experience a force due to itself

What does the value of the electric field depend on?

The distance from which you are measuring; from your position to the location of the source charges

suppose an object is experiencing an electric field with a magnitude of E at its location. if the charge on the object is doubled what happens to the electric field that the object is experiencing?

The electric field that the object is experiencing is unchanged

A disk of radius 0.10 m is in a uniform electric field E and the disk's normal vector is oriented at 30 to the electric field, as shown in the figure. If the disk is rotated clockwise such that its normal vector is parallel to the electric field, what will be the electric flux through the disk?

The electric flux through the disk will be a positive maximum value

A positive point charge q is surrounded by an imaginary sphere of radius r, centered on the charge, as shown in the figure. Compare the electric flux through this sphere to the electric flux through an imaginary sphere of radius 2r, if it enclosed the same charge q.

The electric flux through the sphere of radius r is equal to the electric flux through a sphere of radius 2r

Coulomb's Law

The relationship among electrical force, charges, and distance: The electrical force between two charges varies directly as the product of the charges and inversely as the square of the distance between them.

Coulomb's Law is subject to the conservation of charge and therefore the conservation of energy (T/F)

True, energy is always conserved in closed systems