circuits and magnetism Flashcards by Maddi Clark

electrostatics

study of electromagnetic phenomena at equillibrium (when particles are not moving)

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charge

causes matter to experence force in an electric field
measured in colloumbs

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magnitude of both proton and electron charges

1.6E-19

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conservation of charge

no protons/ electrons are created or destroyed

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coloumbs law

F = Kq1q2/r^2
k is 8.99E9

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electric field

region where a charge feels a force

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force in an electric field eqn

F= E*q

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electric field equation

E= F/q

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units of electric field

C/N or V/m

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field lines

graphically represent electric fields

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what does the number of electric field lines represent

relative strength of electric field

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electric field eqn in terms of columbs law

E = Kq1/r^2

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which way do positive charges cause fieldlines to point

outward

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which way do negative charges cause fieldlines to point

inward

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current (I)

charge flows through a conductor in a specific direction
charge over time: C/s or A

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direct current

1 direction throgh a circuit (batteries)

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alternating current

direction of current flow changes

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what drives current movement

voltage differentials

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voltage

measure of electric potential difference

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electromotive force

voltage difference that powers current movement

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resistance eqn

R= ρ*L/a
ρ is inherit resistance of object

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what does resistance depend directly on

length

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what does resistance depend indirectly on

inverse of area

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resistors

reduce current flow in a circuit and transform KE into other usable forms of energy like light and heat

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ohms law

V=IR

ohms law (i)

V/r= I

what is current proportional to

voltage

what is current inversely related to

resistance

ohms law (r)

R= V/I

resistance defn

units of ohms volts/ amperes

voltage def

electrical potential energy of a charge at a given point in the electric field divided by the charge V= U/q

work performed in terms of voltage and charge

W = V*q

power of circuit equation

V*q/t or V*I - power is voltage times curren t

power eqn in terms of resistance and current

P=I^2R

power eqn in terms of resistance and voltage

v^2/R = P

voltage drop

voltage moves from + to -

resistor in a circuit diagram

sqwiggles

resistance of conductive wire

very low, negligable

Kirchoff's laws

adaptations of conservation of mass/ energy in context of electrical circuits

kirchoffs first law

any junction in circuit, sum of current entering the junction must equal the sum of currents exiting the junction Iin= Iout

kirchoff's 2nd law

for a closed system, the sum of voltage drops throughout the circuit = the source voltage (emf) Vsource = Sum of voltage

series resistors

add one after the other in a row - uninterrupted flow of charge

parallel resistors

- current in split among resistors

what happens to current in resistors in series

carry same current throughout I1= 12

what happens to resistance in series

R1 + R2 + R3

what happens to voltage in resistance in series

V + v2+ v3

what happens to current in resistance in parallel

I1+ I2 + I3

what happens to resistanc ein parallel

1/R + 1/R = 1/R total

what happens to voltage in parallel

V= v2 = v3

how does resistance add in parallel

reciprocally

how does resistance add in series

directly

what measures current

ammeters

voltmeter

measures voltage

ohmmeters

measure resistance

capacitor

device containing two separate components with opposite charge 2 parallel conductive plates seperated by an insulator

dielectric material

insulating material between conudctive plates of a capacitor

capacitance

amount of charge stored in a capacitor for a given voltage units : F

capacitance eqn

C=Q/V

charge in terms of capacitance and capacitance

Q= C*V

ways to increase charge in a capacitor

1. increase the voltage 2. increase the capacitance

units of capacitance

F or C/V

what factors affect capacitance

1. geometry of the capacitor 2. insulatory (dielectric) material seperating the two charged plates

capacitance (geometry) eqn

C= ε0*a/d a is overlapping cross sectional area of the plates ε0 is permitivity of free space 8.85E-12 d is distance between charged plates

what is the purpose of an insulator in a capacitor

prevent the charges on the plates from equalizing

dielectric constant

K= ε/ε0 - greater dielectric constant = more charge the capacitor can store at a given voltage

capacitance in terms of charge and voltage

C= Q/V

C' = C*K modified capacittance when capacitor leaves a vaccum

electric field in terms of voltage and distance

E=V/d - only applies to uniform electric fields

Electric field eqn in terms of force

E=f/q

potential energy (capacitance)

PE= .5CV^2

capacitors in series

1/ctotat = 1/c +1/c

capaciters in parallel

Ctotal = c1 + c2 + c3

relationship between capacitors and resistors in series or parallel

reverse series: C is 1/c and R is R + R

does charge flow across capacitors

if you increase surface area what happens to capacitance

increase

magnetism

force exerted when magnets repel or attract one another

magnetic fields

magnetic fields are like electric fields BUT they only act on moving charges unit - T

tesla (T)

magnitude of magnetic field throuh which a particle with a charge of 1 C moving perpendicular to the field a 1 m/s a force of 1 N

how are magnetic fields generated

1. by magnetic materials 2. moving charges

dimagnetic

materials paired with electrons do not generate a magnetic field and cannot be magentized - fabric, glass, etc

paramagnetic

unpaired electrons have random spins, and the material as a whole has no magnetic dipole

ferromagnetic

materials with unpaired electrons with random spin that can be permanently affected by the application of an external magnetic field - everyday magnet

magnets always have

a positive and negative end

magnetic field lines

behave like electric field lines and point toward negative dipoles

strength of magnetic field with current moving through a wire

B= µ o*I/(2πr) uo is permiability of free space I is current r distance from wire

what is B directly proportional to

current

what happens to b as r is increased

magnetic field decreases

how to determine direction of magnetic field

right hand rule thumb direction of current fingers curve in direction of field

force exerted by magnetic field

Fb = qVBsintheta

right hand rule for force of magnetic field

thumb- direction of charge fingers - direction of field force is palm (up is +/ down is -)

force is always ____ to particle motion

perpindicular

radius of a charged particle in a magnetic field

r= mv/qB

magnetic force on a current carrying wire

Fb = I*L*B sintheta