exam 2 Flashcards
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Capictors in series
1/Ceff=ε/Q=1/C1+1/C2+1/C3…
How to increase capacitance?
Increase the area of the plate
Use diaelectrics (insulator with polarized molecules in between so that E field in between plates becomes weaker)
Energy Storage in a capacitor
U= QV/2
Capcitance general formula
C=Q/V where Q is charge moved and V is volatage (epsilon)
Capactitors strategies
label everything really really well and stay consistent
Identify capacitors in series and parallel and combine
Ohms law for voltage
V=IR
Time constant RC cricuit
Tau=RC
Magnetic F on a moving charge
Formula and direction
F=qV×B
The F is perpendicular to both the velocity of the charge and the magnetic field
Magnetic flux
∫∫B*dA=0
Radius for circular motion of particle
r= mV/qb
Period for circular motion of particle
T=2pim/qB
Frequency
1/T=qB/2pim
Capacitors in parallel
Ceff=Q/ε=C1+C2+C3…
Resistors in series
Rseries =R1+R2+R3… (opp of capacitance in series)
Resistors in parallel
1/Rparallel=1/R1+1/R2+1/R3…
RESISTORS IN PARALLEL HAVE THE SAME VOLTAGE
Finding voltage RC circuit
FIRST-consider initial conditions @t=0
THEN what happens when t->infinity
use loop law
consider = voltage drop given by Ohm’s law
Resistivity
R= pL/A
Resistivity depends on the material, the length (the longer the object the larger the resistance)
Electric power (P)
dissapted through resistor
P=IV
P=I^2R
since V=IR
Current def (I)
I=dq/dt
Current understanding
I=nqvdA
where n is the number of charge carriers, q is the charge, v is the drift velocity, and dA is cross sectional area
Magnetic force on a current
F(vector)=I L*B (take cross product of vectors L and B)
Hall voltage
VH= vBh
Lorentz force
F=qE+qV*B
Magnitude of velocity for particle under influence of both Fe and Fm
V= E/B
Parallel Resistors have the same…
Voltage (V)
Resistors in series have the same…
Current (I)
If V0=E/B and if the three vectors are pointing perpendicular to each other in the appropriate directions
then the charged particle will travel in a straight line without deflection
Voltage on a current over time in an RC circuit
Vc (t) =esplison (1-e^(-t/tau))
Loop law RC charging
Vc+Vr=epsilon
Loop law Rc discharging
Vc+Vr=0
V of resistor over time because of the loop law
start with loop law Vr+Vc=epsilon
Vr=epsilon-Vc
Start with epsilon and decreases exponentially
Flow of current in a RC current
Battery moves (+) charges from one side of capacitor to other side of the capacitor, travels through resistor on the way there
Elecrtic potential
U=Vq
think like potential energy -> can all convert to kinetic energy
Charge change when discharging a capcacitor
Q(t)= Q0 (e−t/ τ)
Energy stored on a capacitor
U=Q^2/2C
Capacitors in parallel have the same
Voltage (V)
Capacitors in series have the same
charge (Q)
Capacitance of parallel plate capacitors
C= epsilon A/d
Energy density of an electric field
nu=1/2 epsilon E^2
Current density
=I/A
