Final Exam 108 Flashcards
Amphere’s law in words
Magnetic field created by an electric current
Amphere’s Law formula
Line integral Bdl =muoI (encircled)
2 Criteria for choosing Ampherian Loop and any explanation
- Loop needs to pass through field pt
- Direction of loop needs to be either ⊥ or || to B vector
2 why-> parallel dlB=dl(B)
perdendicular dlB=-0
Solenoid B field lines
B field lines are parallel lines inside the solenoid
Lenz law
Dircetion of induced emf is such that the magnetic field created by the induced current opposes the change in magnetic flux
Magnetic flux
flux= double integral B*dA
Biot-Savart law in words
A current element creates a magnetic field
Biot-Savart
dB= munaught/4pi * I dl (vector) *rhat/ r^2
Gauss law in words
E-field created by a charge that enters normal to an area
Faraday’s law in words
When there is a change in flux, coil will induce an emf to oppose that change
Faraday’s Law of Induction
ε=-d(mag flux)/dt
What does the induced emf do?
Can cause a current to flow just not localize
Induced current according to Faraday’s law of induction
I induced = ε/R
Lorentz force
F= qE+qV*B
Hall Voltage
Vh=vBh
Generic B field created by an infinately straight current (formula and direction of field lines)
B=(munot*I)/(2pir)
Field lines are circles around current
Parallel Currents
Attract eachother
Anti-Parallel Currents
Repel eachother
Energy Stored in a inductor
U=0.5 LI^2
What faraday’s law does
Induced emf (electric field) created by by a changing flux which comes from a change in B field
Electric dipole
p=qd
Potential energy of electric and magentic dipole
dot product use cos(theta) bc results in scalar
Lenz law
If flux entering a current loop, have to determine direction of current given that the b field from current will oppose flux
R series
Rs= R1+R2+R3…
R parallel
1/Rp= 1/r1 +1/r2 +1/r3…
Capacitors in series
Cs= 1/C1 + 1/C2 +…
Definition of resistance
R= resisitivty constant (Ro) L/A
Definition of capacitance
C=Enaught (A/d)
Force on a test charge
F=qE
B field through a solenoid
munaughtnI
Faraday’s law of induction
Use Ohms law
Iinduced =V/R
Energy Storage in a capacitor
U= QV/2
Period for circular motion of particle
T=2pim/qB
Frequency
1/T=qB/2pim
Radius for circular motion of particle
r= mV/qb
Electric power (P)
dissapted through resistor
P=IV
P=I^2R
since V=IR
Magnetic force on a current
F(vector)=I L*B (take cross product of vectors L and B
Magnitude of velocity for particle under influence of both Fe and Fm
V= E/B
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)
Resistors in series
have the same I
Resistors in Parallel
RESISTORS IN PARALLEL HAVE THE SAME VOLTAGE
Gauss law plane
sigma/2epsilon
Gauss law sphere
Q/4piepsilonr^2
Gauss law cylindrical
E=lambda/2piepsilonr
Current definition
I = qvnA
B field of current loop
B=unaught*i/2R
