Magnetism and Electric Fields

Question 1

magnetic fields

Answer 1

vector quantities that represent the magnetic influence on an electrical charge of other moving charges or magnetized components

Question 2

Sources of magnetic fields

Answer 2

electromagnetic radiation, permanent magnets, electrical current

Question 3

magnetic fields from MRI come from

Answer 3

sequential conductive coil of current flowing in a circular direction

Question 4

Capacitance

Answer 4

ability to store electric charge at small distances from one another, generates voltage

does not generate magnetic field

C=Q/V (farads)

Question 5

charged particles

Answer 5

generate an electric field that exerts force on other surrounding charged particles

Question 6

Lorentz force

Answer 6

exerts a moving charge in the presence of a magnetic field that is perpendicular to a particle’s velocity

trajectory is forced into a curved path with negative and positive charges bent in opposite directions

Question 7

dielectrics

Answer 7

polarizable materials in which electric dipoles can be induced

decreases electric field and voltage, increasing capacitance

K = dielectric constant

Question 8

capacitance equation

Answer 8

C=Q/V (farads)

charge/voltage

Question 9

Electrostatic forces

Answer 9

known as Coulomb forces
it is the attractive or repulsive forces between two electrically charged objects
when charges are unbalanced, they become unstable

Question 10

Coulomb’s Law equation

Answer 10

F = Kq1q2/r^2

k = 8.99 x 10^9 Nm^2/C^2

Question 11

Insulators

Answer 11

keep charge to one location and do not transfer charges

electrons do not flow freely; very little electric current

Question 12

Conductors

Answer 12

evenly space out charges within the system
transfer and transport charges
used in circuits and electrochemical cells

ex: metals and ionic solutions

Question 13

Electric Fields

Answer 13

exert forces on other charges that move into the space of the field

E = kQ/r^2=Fe/q

E = ΔV/d

dividing coulomb’s law by “q”

Question 14

Electric Potential Energy

Answer 14

U = kq1q2/r

like charges will cause a positive potential energy; with objects becoming more stable the further apart they are

opposite charges will have a negative potential energy; with objects becoming more stable the closer they are

Question 15

Electric Potential energy definition

Answer 15

how much energy you need to move a charge against an electric field

ex: when I try to push the positive part of magnets together I have to put in a lot of energy to get them close to one another

Question 16

magnetic force

Answer 16

Fb = qvBsinθ

charges must have a perpendicular component of velocity in order to experience a magnetic force

Question 17

What happens if a charge is moving parallel to the magnetic field vector?

Answer 17

No magnetic force will be experienced. Magnetic forces only work when there is a perpendicular component of velocity

Question 18

What is the charge of a proton?

Answer 18

1.6 x 10^-19C

Question 19

centripetal force equation

Answer 19

mv^2/r

Question 20

What is the speed of light?

Answer 20

c = 3 x 10^8 m/s

λf=c

Question 21

equation for energy of a photon

Answer 21

E = f x h

h = plank's constant = 4 x 10^-15 eV*s
h = 6.626 x 10^-34 kg m^2/s

E = ch/λ

Question 22

electrical fields move?

Answer 22

transverse, perpendicular to each other

Question 23

where is static electricity more significant?

Answer 23

in drier air because lower humidity makes it easier for charge to become and remain separated

Question 24

coulomb unit

Answer 24

1.6 x 10^-19 C = e

1 C = 6.24 x 10^18 e

amount of energy each proton and electron have

Question 25

Electric potential equation

Answer 25

V = kQ/r when Q is positive, V is positive when Q is negative, V is negative

Question 26

Electric potential voltage equation

Answer 26

ΔV = Vb-Va = W/q change in electric potential is the work it takes to bring object from infinity to point in electric field/magnitude to charge when there is low potential energy because close to the oppositely charged plate, will have low electric potential. (opposite case when same charge) ``` W = negative when decrease in electric potential energy W = positive when increase in electric potential energy ```

Question 27

How will a negative test charge move spontaneously through electric field?

Answer 27

move from lower electric potential to higher electric potential positive test charge will move spontaneously move in direction that decreases their electric potential

Question 28

what sign would W be if moving positive q from high to low electric potential?

Answer 28

W would be negative because moving with the electric fields does not require additional energy from Work and therefore would be a decrease is potential energy

Question 29

What sign would W be if moving positive q from low to high electric potential?

Answer 29

W would be positive because work is required to move something against the concentration gradient. This would be an increase in potential energy

Question 30

What is a high electric potential for a positive q

Answer 30

moving closer to another positive q would result in high electric potential because highly repulsive

Question 31

electric dipole

Answer 31

2 equal and opposite charges being separated a distance d can be transient like london dispersion forces or permanent like water and carbonyl groups

Question 32

electric dipole moment equation

Answer 32

P = qd C*m units

Question 33

net torque on dipole equation

Answer 33

T = pE sin Θ ``` T = torque p= dipole moment e = magnitude of uniform external electric field ```

Question 34

diamagnetic

Answer 34

atoms with no unpaired electrons no net magnetic field slightly repelled by magnet includes things you don't expect will get stuck to magnet: water, glass, plastic, skin, and wood

Question 35

paramagnetic

Answer 35

atoms with unpaired electrons has a net magnetic field weakly magnetized in presence of external magnetic field aluminum, copper, and gold

Question 36

ferromagnetic

Answer 36

unpaired electrons permanent atomic magnetic dipole strongly magnetized when exposed to magnetic field iron, nickel, and cobalt bar magnets are ferromagnetic with north and south pole

Question 37

magnetic field equation

Answer 37

B = μI/2πr μ=permeability of free space (4π x 10^7 T*m/A) I = current for a circular loop, don't need pi

Question 38

magnetic field equation for straight wire

Answer 38

Fb = ILBsinΘ ``` I = current L = length B = magnetic field ```

Question 39

How are J, C, and V related?

Answer 39

1 J = C * V 1 V = J/C 1C = J/V

Question 40

Law of conservation of charge

Answer 40

net charge of an isolated system remains constant ex: when ions are added to a neutrally charged solvent like water, the overall solution remains the same

Question 41

How can you change the net charge of a system?

Answer 41

Introduce a charge from elsewhere or remove a charge from the system

Question 42

electrostatic induction

Answer 42

charged object induces the movement/redistribution of charges in another object something positive will cause all the positive charge to move away and the negative charge to move closer. ex: like how a balloon sticks in your hair after you rubbed it on the carpet

Question 43

electric potential

Answer 43

voltage | difference in potential energy per unit charge between two locations in an electric field.

Question 44

units of magnetism

Answer 44

N s / C m = 1 Tesla = 10^4 Gauss

Question 45

charge of electron/proton

Answer 45

1.6 x 10^19 C

Question 46

mass of proton

Answer 46

1.6 x 10^-27 kg

Question 47

mass of electron

Answer 47

9 x 10^-31 kg

Question 48

electrospinning

Answer 48

when electric forces (generated by voltage source) at the surface overcome the surface tension and cause electrically charged jet to be ejected

Question 49

dielectric constant

Answer 49

K ability of a dielectric to increase the capacitance of a parallel plate relative to capacitance of a vacuum C= K * C0 capacitance with dielectric = dielectric constant x initial capacitance