what kind of force does electrostatic forces produce?

repulsive or attractive

ground

a means if returning charge to the earth

why is static charge buildup (static electricity) more significant in drier air?

lower humidity makes it easier for charge to become and remain separated

coulomb

the SI unit for charge;

e=1.60 x 10^-19 C, value for proton and electron

law of conservation of charge?

charge can neither be created nor destroyed

insulator

will not easily distribute a charge over its surface and will not transfer that charge to another neutral object very well; tend to be nonmetals

dielectric material

in electric fields, these materials do not allow electric charges to flow through them; insulators

conductor

when given a charge, these will distribute approximately evenly upon the surface if the conductor, able to transfer and transport charges. usually material with more free electrons; metals

coulomb’s law

quantifies the magnitude of electrostatic force between two charges

Fe= (kq1q2)/ r^2

Fe=electrostatic force

k=coulombs constant (electrostatic constant)

coulombs constant

1/(4pi(eo)) = 8.99 x 10^9 (NxM^2)/C^2

eo= permittivity of free space

electric field

make their presence known by exerting forces on other charges that move into the space of the field; a vector quantity

E=Fe/q=kQ/r^2

what determines in an electric field if the force felt is attractive or repulsive?

it depends on whether the stationary test charge (q=the charge placed in the electric field) and the source charge (Q=what creates the electric field) are opposite charges or like charges

what is the convention of electric field vectors?

the direction of the force in an electric field is given as the direction a positive test charge would move in presence of the source charge. So a source of positive charge gives repulsive forces while a negative source charge gives attractive forces

field lines

imaginary lines that represent how a positive test charge would move in the presence of the source charge

electrical potential energy (U)

U=kQq/r

how does work and electrical potential energy relate?

we can define electrical potential energy for a charge at a point in space in an electric field as the amount of work necessary to bring the charge from infinitely far away to that point

electrical potential (V)

not the same a U and is a scalar quantity, sign is determined by the source charge Q. the work necessary to move a test charge from infinity to a point in space in an electric field surrounding a source charge

V= U/q or V=kQ/r (when not test charge present)

units: volts (V)= 1 J/C

voltage

the potential difference between two electrical points a and b

deltaV=Vb-Va= Wab/q

Wab

the work needed to move a test charge q through an electric field from point a to point b

what is the direction that a positive test charge will move? what about a negative test charge?

- a positive test charge will move from position of higher electrical potential to a position of lower electrical potential= voltage will be negative here
- a negative test charge will spontaneously move form a position of lower electrical potential to a position of higher electrical potential=voltage will be positive here

equipotential line

a line on which the potential at every point is the same, in a 3D image, the lines create a sphere around the source

electrical potential near a dipole

V=(kqd)cos/ r^2

dipole moment (p)

the product of charge and separation distance; a vector. In chem the dipole points from positive to negative while physics has dipole point from negative to positive

SI unit: Cxm

p=qd

perpendicular bisector of the dipole

any point that lies along the plane that is halfway between +q and -q (perpendicular to these) will have an electrical potential of zero

electric field on the perpendicular bisector of a dipole

E=1/(4pi(eo))xp/r^3

or

E=kp/r^3

p=dipole moment (point in direction according to physics, negative to positive)

net torque on a dipole

t=pEsin(theta)

p=dipole moment

E=magnitude of the external electrical field

theta=the angle the dipole moment makes with the electric field

magnetic fields

created by magnets and moving charges; unit is tesla (T)= Ns/mC and 1 T= 10^4 gauss

diamagnetic

materials made of atoms with no unpaired electrons and that have no net magnetic field, slightly repelled by a magnet and so can be called weakly antimagnetic

paramagnetic

have unpaired electrons, become weakly magnetized in the presence of an external magnetic field aligning the magnetic dipoles of the material with the external field

ferromagnetic

have unpaired electrons; will become strongly magnetic in an external magnetic field or under certain temps

magnetic field from a straight wire

B= (uo)I/(2pir)

B=magnetic field at a distance r from the wire

uo=permeability of free space (4pix10^-7 Tm/A)

I=current

magnetic field from a loop of wire

B= (uo)I/(2r)

B=magnetic field at a distance r from the wire

uo=permeability of free space (4pix10^-7 Tm/A)

I=current

which way do the field lines point in magnets?

field lines point from the north to the south pole

Lorentz Force

the sum of electrostatic and magnetic forces

magnetic force on a moving point charge

Fb=qvBsin(theta)

Fb=magnetic force q=charge v=velocity B=magnitude of the magnetic field theta= smallest angle between the velocity vector v and the magnetic field vector B

magnetic force on a current carrying wire

Fb=ILBsin(theta)

Fb=magnetic force I=current L=length of the wire B=magnitude of the magnetic field theta= angle between L and B

in the right hand rule, current is considered the flow of positive charge (v)