Chapter 15 questions Flashcards
A suspended object A is attracted to a neutral wall. It is also attracted to a positively charged object B. What do we know about the charge of A?
It is negatively charged
Object A has a charge of 2 microcoulombs and object B has a charge of 6 microcoulombs. What do we know about the relationship between Fab and Fba?
Fab = -Fba
‘equal and opposite’
A test charge of three microcoulombs is at point P where the electric field due to other charges is directed to the right and has a magnitude of 4E6 N/C. If the test charge is replaced with a charge of negative three microcoulombs, what happens to the electric field at point P?
the field remains the same
A circular ring of charge of radius b has total charge q uniformly distributed around it. What is the magnitude of the electric field at the center of the ring?
ZERO - all charges cancel out
A free electron and a free proton are placed in an identical electrical field. What do we know about their behavior? (2 statements)
the magnitude of the acceleration of the electron is greater than that of the proton (F=ma OR a=F/m)
The electric force on the proton is equal in magnitude to the electric force on the electron, but in the opposite direction
What do we know about the magnitude of an electric field based on the field lines?
field lines that are close together = stronger electric field
field lines that are farther apart = weaker electric field
Calculate the magnitude of the flux of a constant electric field of 5 N/C in the z direction through a rectangle with area 4m^2 in the xy plane
PHI=EAcos(theta)
PHI= 20 Nm^2/C
Calculate the magnitude of the flux of a constant electric field of 5 N/C tilted 60 degrees away from the positive z direction through a rectangle with area 4m^2 in the xy plane
PHI = EAcos(theta)
PHI = 10 Nm^2/C
When calculating flux, do positive and negative charges cancel out when tallying them up?
YES
For a closed surface through which flux is zero, there are two statements which must be true. What are they?
the net charge inside the surface is zero
the number of electric field lines entering the surface is equal to the number that leaves the surface
A glass object receives a positive charge by rubbing it with a silk cloth. In the rubbing process, have protons been added to the object or have electrons been removed from it?
electrons have been removed
The fundamental charge is e = 1.60E-19 C. Is it possible to transfer electric charge to an object so its net charge is 9.5 times the fundamental electric charge e?
no, charge is quantized
All protons have a charge of +e. True or false?
true
True or false? Electrons in a conductor have a charge of -e while electrons in an insulator have no charge.
False
The net charge is always zero _____ the surface of an isolated conductor
inside
The electric field is always zero ______ a perfect conductor
inside
The charge density on the surface of an irregularly shaped, isolated, charged conductor is highest where the surface is ______
sharpest
Two uncharged conducting spheres are separated by distance d. When charge -Q is moved from sphere A to sphere B, the coulomb force has magnitude Fo. Is the coulomb force attractive or repulsive?
attractive
Two uncharged conducting spheres are separated by distance d. When charge -Q is moved from sphere A to sphere B, the coulomb force has magnitude Fo. If an additional charge -Q is moved from A to B, what is the ratio of the new coulomb force to the original coulomb force Fnew/Fo?
4
note F=ke(q1q2/r^2)
q1=+2 and q2=-2
Two uncharged conducting spheres are separated by distance d. When charge -Q is moved from sphere A to sphere B, the coulomb force has magnitude Fo. If sphere B is neutralized so it has no net charge, what is the ratio of the new to the original coulomb force Fnew/Fo?
0
Positive charge Q is located at the center of a hollow, conducting spherical shell. Is induced charge Qinner on the inner surface of the shell positive or negative?
negative
Positive charge Q is located at the center of a hollow, conducting spherical shell. Is the induced charge Qouter on the outer surface of the shell positive or negative?
positive
Positive charge Q is located at the center of a hollow, conducting spherical shell. What is the ratio of Qinner/Q?
-1
Positive charge Q is located at the center of a hollow, conducting spherical shell. What is the ratio of Qouter/Q?
1
Consider a point located an arbitrary distance between two point charges in otherwise empty space. The point is not located on a field line. Is it possible for an electric field to exist at the point in empty space?
Yes
Consider a point located an arbitrary distance between two point charges in otherwise empty space. The point is not located on a field line. Does charge exist at that point?
No
Consider a point located an arbitrary distance between two point charges in otherwise empty space. The point is not located on a field line. Does a force exist at that point?
No
A spherical surface surrounds a point charge Q. Describe what happens to the total flux through the surface if the following happens. The charge is tripled.
The flux is tripled
A spherical surface surrounds a point charge Q. Describe what happens to the total flux through the surface if the following happens. The volume of the sphere is doubled.
the flux remains constant
A spherical surface surrounds a point charge Q. Describe what happens to the total flux through the surface if the following happens. The surface is changed to a cube.
the flux remains constant
A spherical surface surrounds a point charge Q. Describe what happens to the total flux through the surface if the following happens. The charge is moved to another location inside the surface.
The flux remains constant
A spherical surface surrounds a point charge Q. Describe what happens to the total flux through the surface if the following happens. The charge is moved outside the surface.
The flux goes to zero
If more electric field lines leave a gaussian surface than enter it, what can you conclude about the net charge enclosed by the surface?
The surface must enclose a positive net charge (field lines go FROM positive charges TO negative charges)
What happens when a charged insulator is placed near an uncharged metal object?
They attract each other
