physics concepts questions exam one
A "free" electron and a "free" proton are placed in an identical electric field. Which of the following statements are true? (Select all that apply.) a. The magnitude of the acceleration of the electron is greater than that of the proton. b. The electric force on the proton is greater in magnitude than the electric force on the electron, but in the opposite direction. c. Both particles have the same acceleration. d. The electric force on the proton is equal in magnitude to the electric force on the electron, but in the opposite direction. e. Each particle is acted upon by the same electric force and has the same acceleration.
A and D
electric flux
A measure of how much the electric field vectors penetrate through a given surface
Rank the magnitudes of the electric field at points A, B, and C in the figure below, with the largest magnitude first.
A, B, C
grounded
Allowing charges to flow directly from the circuit to the ground connection
For a closed surface through which the net flux is zero, each of the following four statements could be true. Which of the statements must be true? (Select all that apply.) A. There are no charges inside the surface. B. The net charge inside the surface is zero. C. The electric field is zero everywhere on the surface. D. The number of electric field lines entering the surface equals the number leaving the surface.
B and D
charging by induction
Charging an object without direct contact between the object and a charge
A point charge q is located at the center of a spherical shell of radius a that has a charge −q uniformly distributed on its surface.Find the electric field for the following points: (a) for all points outside the spherical shell
E = 0
A point charge q is located at the center of a spherical shell of radius a that has a charge −q uniformly distributed on its surface.Find the electric field for the following points: (b) for a point inside the shell a distance r from the center
E = kq/r2
Object A has a charge of +2 µC, and object B has a charge of +6 µC. Which statement is true?
F(AB)= - F(AB)
A suspended object A is attracted to a neutral wall. It's also attracted to a positively charged object B. Which of the following is true about object A?
It has a negative charge.
A spherical surface surrounds a point charge q. Describe what happens to the total flux through the surface if the following happens: (e) The charge is moved outside the surface.
The flux goes to zero.
A spherical surface surrounds a point charge q. Describe what happens to the total flux through the surface if the following happens: (a) 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: (b) 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: (c) 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: (d) The charged is moved to another location inside the surface.
The flux remains constant.
superposition principle
The resultant force on any one charge equals the vector sum of the forces exerted by the other individual charges that are present.
Electrostatics
The study of forces between stationary electric charges
If more electric field lines leave a Gaussian surface than enter it, what can you conclude about the net charge enclosed by that surface?
The surface must enclose a positive net charge.
electric field
a field of force surrounding a charged particle
charges with opposite signs ______ each other
attract
charging by contact (conduction)
charging an neutral object by contact with a charged object
magnitude of force _________ with separation distance
decreases
conservation of electric charge
electric charge can neither be created nor destroyed
Coulomb's Law
electric force between charged objects depends on the distance between the objects and the magnitude of the charges.
dipole configuration physics
from positive to negative
insulators
materials in which any excess electric charges remains localized and does not move freely in the space between atoms. electrons are tightly bound
conductors
materials in which electron charges move freely in response to an electric force. electrons are loosely bound
The object that gains electrons becomes _______ charged
negatively
if "q" is negative, the electric force on it is in the __________ direction as E (electric field)
opposite
electromagnetic force
physical interaction that occurs between electrically charged particles
the object that loses electrons becomes ___________ charged
positively
Vectors
quantities that have both a magnitude and a direction
negative fields point _______
radially inward (sinks)
positive fields point ______
radially outward (sources)
charges with the same sign _____ each other
repel
if "q" is positive, the electric force on it is in the __________ direction as E (electric field)
same
order of the fundamental forces strength
strong force -> electromagnetic -> weak force-> gravity
Gauss's Law
the electric flux through a closed surface is equal to the net charge Q inside the surface divided by E not
Find the electric flux through the surface in the figure below. Assume all charges in the shaded area are inside the surface.
−(6 C)/ε0
