Electrostatics and Magnetism Flashcards Preview

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Flashcards in Electrostatics and Magnetism Deck (36)
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1
Q

what kind of force does electrostatic forces produce?

A

repulsive or attractive

2
Q

ground

A

a means if returning charge to the earth

3
Q

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

A

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

4
Q

coulomb

A

the SI unit for charge;

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

5
Q

law of conservation of charge?

A

charge can neither be created nor destroyed

6
Q

insulator

A

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

7
Q

dielectric material

A

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

8
Q

conductor

A

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

9
Q

coulomb’s law

A

quantifies the magnitude of electrostatic force between two charges
Fe= (kq1q2)/ r^2

Fe=electrostatic force
k=coulombs constant (electrostatic constant)

10
Q

coulombs constant

A

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

eo= permittivity of free space

11
Q

electric field

A

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

12
Q

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

A

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

13
Q

what is the convention of electric field vectors?

A

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

14
Q

field lines

A

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

15
Q

electrical potential energy (U)

A

U=kQq/r

16
Q

how does work and electrical potential energy relate?

A

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

17
Q

electrical potential (V)

A

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

18
Q

voltage

A

the potential difference between two electrical points a and b

deltaV=Vb-Va= Wab/q

19
Q

Wab

A

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

20
Q

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

A
  • 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
21
Q

equipotential line

A

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

22
Q

electrical potential near a dipole

A

V=(kqd)cos/ r^2

23
Q

dipole moment (p)

A

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

24
Q

perpendicular bisector of the dipole

A

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

25
Q

electric field on the perpendicular bisector of a dipole

A

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

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

26
Q

net torque on a dipole

A

t=pEsin(theta)

p=dipole moment
E=magnitude of the external electrical field
theta=the angle the dipole moment makes with the electric field

27
Q

magnetic fields

A

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

28
Q

diamagnetic

A

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

29
Q

paramagnetic

A

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

30
Q

ferromagnetic

A

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

31
Q

magnetic field from a straight wire

A

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

32
Q

magnetic field from a loop of wire

A

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

33
Q

which way do the field lines point in magnets?

A

field lines point from the north to the south pole

34
Q

Lorentz Force

A

the sum of electrostatic and magnetic forces

35
Q

magnetic force on a moving point charge

A

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
36
Q

magnetic force on a current carrying wire

A

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)