Ch 21: Electric Charge and Electric Field Flashcards
principle of conservation of charge
the algebraic sum of all the electric charges in any closed system is constant
The charge on any macroscopic body is always either ___ or ___.
zero or an integer multiple (negative or positive) of the electron charge
conductor
substance that permits the flow of charge
insulator
substance that does not readily conduct electricity
Most ___ are good conductors.
metals
Most ___ are insulators
nonmetals
charging by induction using a negatively charged object
when you bring a negatively charged object close to a neutral object, positive charges build up on the side closest to the charged object and negative charges build up on the opposite side
polarization
an effect caused by a slight shift of positive and negative electric charge in opposite directions within an insulator
Coulomb’s Law (in words)
the magnitude of the electric force between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them
Coulomb’s Law (in math)
F = k|q_1 q_2| / r^2
The direction of the forces tow charges exert on each other are always along ___.
the line joining them
When 2 charges have the same sign, the forces they exert on each other are ____.
repulsive
When 2 charges have opposite signs, the forces they exert on each other are ____.
attractive
The two forces 2 charges exert on each other obey ___ because ___.
Newton’s 3rd law; they are always equal in magnitude and opposite in direction, even when the charges are not equal in magnitude
coulomb
SI unit of electric charge
In Coulomb’s Law, what is k equal to?
1/4πϵ_0
When 2 charges exert forces simultaneously on a third charge, the total force acting on that charge is ___.
the vector sum of the forces that the two charges would exert individually (principle of superposition of forces)
An electric field is a consequence of ___ only.
the charge on a body in the area
The electric force on a charged body is exerted by ___.
the electric field created by other charged bodies
electric field (at a point)
the electric force experienced by a test charge q_0 at the point, divided by the charge q_0; electric force per unit charge; E=F/q
units of electric field
N/C
force exerted on a point charge by an electric field
F = qE
If q is positive, then the force experienced by the charge is in the ___ direction as/of the electric field.
same
If q is negative, then the force experienced by the charge is in the ___ direction as/of the electric field.
opposite
vector equation of electric field
E = kq/r^2 rhat
The electric field of a point charge always points away from a ___ charge and toward a ___ charge.
positive; negative
The electric field at every point within the material of a conductor must be ___.
zero
principle of superposition of electric fields
the total electric field at a point is the vector sum of the fields at that point due to each point charge in the charge distribution
electric field line
an imaginary line or curve drawn through a region of space so that its tangent at any point is in the direction of the electric field vector at that point.
When the electric field is strong, the electric field lines are drawn ___.
closely together
When the electric field is weak, the electric field lines are drawn ___.
farther apart
T/F: Field lines can intersect.
FALSE
T/F: The magnitude of the electric field is the same everywhere along a field line.
FALSEEEEE
In a uniform field, the field lines are drawn ___.
straight, parallel, and uniformly spaced
electric dipole
a pair of point charges with equal magnitude and opposite sign separated by a distance
