The Magnetic Field 3 Flashcards
Induction
E fields generated by a varying magnetic flux
Mechanical energy is converted into what for motional emf?
It is converted into power burned over the resistor (electrical energy) - energy is conserved.
induce
gives rise to
What gets induced? (order of induction)
E field induces emf which induces current which induces magnetic field.
Lenz’s Law
The negative sign in Faraday’s law indicates that the polarity of the induced emf is such that the magnetic field due to the induced current opposes the change in magnetic flux through the area enclosed by the current loop
L
Inductance, constant of proportionality
Steady state
no change in flux
Determining direction of self-induced emf
The polarity of the self-induced emf opposes the change in magnetic flux.
How an inductor works
Current I passing through an inductor with N turns produces a flux through the interior of the inductor
Magnetic flux is proportional to what?
both magnetic field and current
Inductance is similar to what?
Capacitance
Like capacitance, inductance is dependent upon…
geometric factors only
Another name for self-induced emf
back emf
Difference between RC and RL circuits
RC circuits - increase/decrease in charge
RL circuits - increase/decrease in current
When the switch is closed to a in a RL circuit, what does the inductor do?
It initially opposes the change in current with a back emf. At t=0s, it behaves like a broken wire. At t=many seconds, it behaves like a connecting wire.
Does the circuit itself have an inductance?
Yes, but it is assumed that the inductance of the inductor is much larger than that of the circuit.
What makes current response slow?
Inductors
Current growth: I(0), Vr(0), VL(0)
I(0)=0, Vr(0)=-IR=0, VL(0)= - epsilon
Energy in a magnetic field like…
Energy in a capacitor
Oscillations in an LC circuit mimmick what?
Simple harmonic motion
In an LC circuit, the energy stored in a capacitor’s electric field is transferred to
the magnetic field of the inductor (after the energy in the electric field generates a current).
Angular velocity units
1 / s
