Ch 21: Electric Charge and Electric Field

Question 1

principle of conservation of charge

Answer 1

the algebraic sum of all the electric charges in any closed system is constant

Question 2

The charge on any macroscopic body is always either ___ or ___.

Answer 2

zero or an integer multiple (negative or positive) of the electron charge

Question 3

conductor

Answer 3

substance that permits the flow of charge

Question 4

insulator

Answer 4

substance that does not readily conduct electricity

Question 5

Most ___ are good conductors.

Answer 5

metals

Question 6

Most ___ are insulators

Answer 6

nonmetals

Question 7

charging by induction using a negatively charged object

Answer 7

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

Question 8

polarization

Answer 8

an effect caused by a slight shift of positive and negative electric charge in opposite directions within an insulator

Question 9

Coulomb’s Law (in words)

Answer 9

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

Question 10

Coulomb’s Law (in math)

Answer 10

F = k|q_1 q_2| / r^2

Question 11

The direction of the forces tow charges exert on each other are always along ___.

Answer 11

the line joining them

Question 12

When 2 charges have the same sign, the forces they exert on each other are ____.

Answer 12

repulsive

Question 13

When 2 charges have opposite signs, the forces they exert on each other are ____.

Answer 13

attractive

Question 14

The two forces 2 charges exert on each other obey ___ because ___.

Answer 14

Newton’s 3rd law; they are always equal in magnitude and opposite in direction, even when the charges are not equal in magnitude

Question 15

coulomb

Answer 15

SI unit of electric charge

Question 16

In Coulomb’s Law, what is k equal to?

Answer 16

1/4πϵ_0

Question 17

When 2 charges exert forces simultaneously on a third charge, the total force acting on that charge is ___.

Answer 17

the vector sum of the forces that the two charges would exert individually (principle of superposition of forces)

Question 18

An electric field is a consequence of ___ only.

Answer 18

the charge on a body in the area

Question 19

The electric force on a charged body is exerted by ___.

Answer 19

the electric field created by other charged bodies

Question 20

electric field (at a point)

Answer 20

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

Question 21

units of electric field

Answer 21

N/C

Question 22

force exerted on a point charge by an electric field

Answer 22

F = qE

Question 23

If q is positive, then the force experienced by the charge is in the ___ direction as/of the electric field.

Answer 23

same

Question 24

If q is negative, then the force experienced by the charge is in the ___ direction as/of the electric field.

Answer 24

opposite

Question 25

vector equation of electric field

Answer 25

E = kq/r^2 rhat

Question 26

The electric field of a point charge always points away from a ___ charge and toward a ___ charge.

Answer 26

positive; negative

Question 27

The electric field at every point within the material of a conductor must be ___.

Answer 27

zero

Question 28

principle of superposition of electric fields

Answer 28

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

Question 29

electric field line

Answer 29

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.

Question 30

When the electric field is strong, the electric field lines are drawn ___.

Answer 30

closely together

Question 31

When the electric field is weak, the electric field lines are drawn ___.

Answer 31

farther apart

Question 32

T/F: Field lines can intersect.

Answer 32

FALSE

Question 33

T/F: The magnitude of the electric field is the same everywhere along a field line.

Answer 33

FALSEEEEE

Question 34

In a uniform field, the field lines are drawn ___.

Answer 34

straight, parallel, and uniformly spaced

Question 35

electric dipole

Answer 35

a pair of point charges with equal magnitude and opposite sign separated by a distance