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Physics > Magnetism and Electric Fields > Flashcards

Magnetism and Electric Fields Flashcards

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1
Q

magnetic fields

A

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

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2
Q

Sources of magnetic fields

A

electromagnetic radiation, permanent magnets, electrical current

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3
Q

magnetic fields from MRI come from

A

sequential conductive coil of current flowing in a circular direction

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4
Q

Capacitance

A

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

does not generate magnetic field

C=Q/V (farads)

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5
Q

charged particles

A

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

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6
Q

Lorentz force

A

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

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7
Q

dielectrics

A

polarizable materials in which electric dipoles can be induced

decreases electric field and voltage, increasing capacitance

K = dielectric constant

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8
Q

capacitance equation

A

C=Q/V (farads)

charge/voltage

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9
Q

Electrostatic forces

A

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

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10
Q

Coulomb’s Law equation

A

F = Kq1q2/r^2

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

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11
Q

Insulators

A

keep charge to one location and do not transfer charges

electrons do not flow freely; very little electric current

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12
Q

Conductors

A

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

ex: metals and ionic solutions

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13
Q

Electric Fields

A

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”

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14
Q

Electric Potential Energy

A

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

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15
Q

Electric Potential energy definition

A

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

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16
Q

magnetic force

A

Fb = qvBsinθ

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

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17
Q

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

A

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

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18
Q

What is the charge of a proton?

A

1.6 x 10^-19C

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19
Q

centripetal force equation

A

mv^2/r

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20
Q

What is the speed of light?

A

c = 3 x 10^8 m/s

λf=c

21
Q

equation for energy of a photon

A

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

22
Q

electrical fields move?

A

transverse, perpendicular to each other

23
Q

where is static electricity more significant?

A

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

24
Q

coulomb unit

A

1.6 x 10^-19 C = e

1 C = 6.24 x 10^18 e

amount of energy each proton and electron have

25
Q

Electric potential equation

A

V = kQ/r

when Q is positive, V is positive
when Q is negative, V is negative

26
Q

Electric potential voltage equation

A

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
27
Q

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

A

move from lower electric potential to higher electric potential

positive test charge will move spontaneously move in direction that decreases their electric potential

28
Q

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

A

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

29
Q

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

A

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

30
Q

What is a high electric potential for a positive q

A

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

31
Q

electric dipole

A

2 equal and opposite charges being separated a distance d

can be transient like london dispersion forces or permanent like water and carbonyl groups

32
Q

electric dipole moment equation

A

P = qd

C*m units

33
Q

net torque on dipole equation

A

T = pE sin Θ

T = torque
p= dipole moment
e = magnitude of uniform external electric field
34
Q

diamagnetic

A

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

35
Q

paramagnetic

A

atoms with unpaired electrons
has a net magnetic field
weakly magnetized in presence of external magnetic field

aluminum, copper, and gold

36
Q

ferromagnetic

A

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

37
Q

magnetic field equation

A

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

38
Q

magnetic field equation for straight wire

A

Fb = ILBsinΘ

I = current
L = length
B = magnetic field
39
Q

How are J, C, and V related?

A

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

40
Q

Law of conservation of charge

A

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

41
Q

How can you change the net charge of a system?

A

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

42
Q

electrostatic induction

A

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

43
Q

electric potential

A

voltage

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

44
Q

units of magnetism

A

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

45
Q

charge of electron/proton

A

1.6 x 10^19 C

46
Q

mass of proton

A

1.6 x 10^-27 kg

47
Q

mass of electron

A

9 x 10^-31 kg

48
Q

electrospinning

A

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

49
Q

dielectric constant

A

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

Physics (8 decks)

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