magnetic circuit and transformers ch 5 Flashcards
What is a circuit
A closed path that allows passage for electric current, magnetic flux and data to flow through it.
Types of magnet
Permanent Magnets are made from alloys of Al,Ni and Co, in which magnetism once
created is retained for long time.
Electromagnets are made by placing coil around magnetic material which forms the
core
Properties of magnet
It attracts small pieces of iron
When freely suspended, it sets itself in a direction such that the North Pole points
towards the North direction and South Pole points towards South direction.
Like poles repel each other and unlike pole attract each other.
Magnetic Induction, magnetic field & magnetic field lines
*Where a magnet can create magnetism in a nearby magnetic material without direct contact.
*The region influenced by a magnet is called a magnetic field
*Magnetic field lines are imaginary lines that represent the path a magnetic object or particle would take if it were free to move in a magnetic field
Magnetic flux,Magnetic flux density and Magnetic Field Strength
*The total number of lines of force in a particular magnetic field is called as magnetic flux. Unit is weber.
*flux per unit area.Unit is Tesla (T).
*Force experienced by a unit north pole place at a point in a
magnetic field is known as magnetic field strength. Unit – N/weber.
Magneto motive force,
*It is the force which tends to produce the flux in the magnetic circuit.
*It is the resistance offered by the material to the passage of magnetic flux through it.
*conducting power for lines of force of magnetic materials as compared to Air. Symbol : μ
Faradays 1st law
change in the magnetic field through a conductor induces an electromotive force (EMF) or voltage across the conductor
Faradays 2nd law
Faraday’s second law of electromagnetic induction states that the magnitude of the induced electromotive force (EMF) in a conductor is directly proportional to the rate of change of magnetic flux through the conductor
Fleming’s Right Hand Rule
Arrange the thumb and the first two fingers of your right hand at right angles to one
another. Let the first finger point in the direction of lines of force, the thumb represents the direction
of motion of a conductor then the second finger will point the direction of induced emf.
Lenz’s Law
the induced current will flow in a direction that creates a magnetic field opposing the original change
Dynamically induced emf and Statically induced emf
*Dynamically induced EMF occurs when a moving conductor or a changing magnetic field causes voltage to be generated in the conductor. It’s like a push of electricity that happens when things move or magnetic fields change.
*It is the creation of voltage in a conductor when it is exposed to a stationary magnetic field. It happens without any movement of the conductor or changes in the magnetic field.
Self Induced emf and Mutually induced emf
*A coil in which a change of current causes an emf to be induced
within the coil itself is known as self inductance.
*It is the property due to which the change in current
through one coil produces an emf in the other coil placed near by is known as mutual
induction.
B-H curve
For zero current H =0 and B=0. Slowly as H increases B also increases.
* After point b if H is increased further B almost remains
constant.
* BH curve will be called Hysteresis curve if it is plotted
for one complete magnetizing cycle.
Residual Magnetism and Coercive Force:
Value of B is not zero for I= 0 and H=0. This non zero value of B is known as Residual Magnetism.
value of magnetic field strength required to wipe out the residual flux density.
Transformer
an electrical device which
transfers power from one circuit to another
circuit without without change in frequency.
