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What is Coloumb's law? (equation) What does it mean?
describes force between two charges
F = k (q1q2) / r
k = 9 x 109
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Coloumb's law resembles what? But?
gravitational force (G)(m 1m 2)/(r 2)
- but, gravitational force is attractive
- electrical force is repulsive
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electric field - in what way are the lines drawn? What does the length of the line indicate?
(+) ----------------> (-)
length = strength
(smaller is stronger)
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What is the electric field created by charge Q?
E = k x (Q)/(r2)
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What is the force felt by charge q in the electric field E?
F = E x q
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What makes and feels the field?
Q makes the field
q feels the field
[F = k x (Qq)/(r2)
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What is the potential energy of of the charge in electric field?
Potential energy (U) = force x displacement (like ugh)
U = Eq x h
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How does potential energy change when moving perpendicular to electric field?
doesn't change
same way that moving parallel to surface of the earth doesn't change gravitational potential energy
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What is an electric dipole?
created by 2 opposite charges with equal magnitude
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(+) and (-) fall/rise to lower/higher potential?
+ charge falls to a lower potential
- charge rises to a higher potential
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high/low potential and +/- potenital
- high potential = + potential
- low potential = - potential
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How do we measure movement of a charge?
current (A)
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So, what is current? (How is it measured)
Coloumbs/second
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Current flows in what direction (relative to potential energy)
current flows from high potential to low potential
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In what direction does current flow (relative to electron flow or electron velocity)?
current moves in opposite direction of e- flow
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conducting electricity: what are good conductors and poor conductors?
- good = allow e- to flow freely [metals]
- poor = hold e- tightly in place [resistors]
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What is induction?
charging a conductor
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circuit equations: current, voltage, resistance, capacitance
V = IR
I = Q/t
C = Q/V
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what is capacitance?
ability to store charge per unit voltage [Q/V]
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voltage is the same thing as...... and it depends on
potential energy
depends on distance
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plates that are further apart will have greater/less voltage and capacitance?
greater voltage
less capacitance
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What is a capacitor?
temporarily stores energy in a circuit
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What is the separation of charges in a capacitor?
emf between the plates
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what is resistance?
resistance to flow of charge
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resistance is directly proportionate to what?
length of wire
[R = density x (length/area)]
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resistance and temperature
resistance increases with temperature
[thermal oscillations impede with flow]
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Kirchoff's Rules:
- amount of current flowing in and out
- voltage around the circuit
-battery
- amount of flow in = amount of flow out
- votalge around any path in circuit must sum = 0
- battery adds energy to circuit
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How does battery add energy to the circuit?
increases voltage from one point to another
(emf = voltage added)
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Diaelectric constant (K)
substance between plates of a capacitor
- -must be insulator to separate charge
- -resists creating EF, in order to store energy
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Resistors in series/parallel
what is constant?
series = add [current is constant]
parallel = 1/R [voltage is constant]
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what is the terminal voltage? (equation)
V = emf - IR
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AC Current - what's going on?
e- don't move in one direction,
they oscillate back and forth
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maximum current and maximum velocity in an AC Current
Vmax = sqrt.(2) x Vmax
Imax = sqrt.(2) x Imax
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What creates a magnetic field?
charging electric field
currents (moving charges) creates the magnetic field
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+ and - of electric field corresponds to what in magnetic field?
north and south
north = + and south = -
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In what direction do magnetic lines point?
north -------> south
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Doess a stronger magnetic field have closer lines, or further apart?
closer lines = stronger fied
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How does the KE of a particle moving through the magnetic field change?
no work done by the magnetic field, means no change in KE due to the magnetic field
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What is magnetic force?
F = q x V x B x sin(0)
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force is applied in what direction relative to both velocity and magnetic field
force is perpendicular to both velocity and magnetic field
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What is the work done by magnetic force?
no work:
because it's perpendicular to velocity
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What way does magnetic field act?
like centripetal force (mv2/r)
because charged particle moves in a circle
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What will move through a magnetic field with a smaller radius: a proton or an electron
electron:
because it has smaller mass [F = mv2/r]
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Right Hand Rule
thumb = direction of current
fingers = direction of magnetic field
palm = direction of force
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What results from a change in magnetic field?
an electrical field
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What happens to the mechanical energy in a magnetic field when it is changed and creates an electric field?
mechanical energy to create the field is dissipated as heat
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What is the magnetic flux?
number of magnetic fields running through the loop
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what does change in magnetic flux do?
induces an emf
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What is a magnetic field generated by?
a moving charge
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moving charge experiences what when moving through a magnetic field?
force = qvBsin0
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In what direction is this force?
perpendicular to velocity and magnetic field (B)
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At equilibrium, in an electric and magnetic field, what is the net force acting on a particle?
0
force from electric field = force from magnetic field
Eq = qvBsin(0)
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How can we find the acceleration or distance of a particle traveling through an electric or magnetic field
F = ma
set force (Eq) or (qvbsin) = mass x acceleration
distance = (1/2)at2
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