Inductors Flashcards
Magnetic flux symbol and unit
Phi, Φ, Tm^2
Magnetic flux equation
Φ=BA
Φ is magnetic flux in Tm^2
B is magnetic field strength in (T)
A is area perpendicular to magnetic field (m^2)
What happens if a magnet moves with respect to a wire or vice versa what occurs
A current will flow
Faradays law
The magnitude of the induced e.m.f. is proportional to the rate of change of magnetic flux (Φ) through the coil or circuit.
Lentz’s Law
The induced current is always in such a direction as to oppose the change that is causing it.
Combined Lentzs law and faradays law equation
E ∝-d Φ/dt
E is the EMF (V)
d Φ/dt is rate of change of magnetic flux in Tm^2s^-1
Inductance equation
E=-Ld Φ/dt
E is the EMF (V) back so negative value
d Φ/dt is rate of change of magnetic flux in Φ s^-1
L is the inductance in H
or E=-LdI/dt
I is current (A)
L, inductance, must always be…
Positive
Energy stored in magnetic field of inductor
E=1/2 LI^2
E is energy (J)
L is inductance (H)
I is current (A)
What is produced when current is self induced
Back emf
Inductive reactance equation
XL =V/I
XL is inductive reactance (ohms)
V is voltage (V)
I is current (A)
A.C. Inductive reactance equation
XL = 2pifL
XL is inductive reactance in ohms
f is frequency is Hz
L is inductance (H)
Why would inductor be preferred to a resistor when delivering energy from a capacitor.
Resistor will dissipate energy whereas capacitor will store energy and later deliver it.
Why time delay for current to reach max value in inductor circuit?
Changing current creates back EMF
Inductive reactance definition
The opposition of an inductor to changing to changing current.
