Unit 4 Chapter 1 : Electromagnetic inductionfptcu.com/Gep Files/physics 2/Lecture 8...
Transcript of Unit 4 Chapter 1 : Electromagnetic inductionfptcu.com/Gep Files/physics 2/Lecture 8...
Unit 4
Chapter 1 : Electromagnetic induction
Dr. Mohamed Adel
Chapter 1 : electromagnetic, mutual and self inductance.
- Scientist Oersted discovered that magnetism could be produced by an electric current passes
through a conductor.
- Scientist Faraday discovered that electric current could be produced by using magnetism and
he called this phenomenon (electromagnetic induction)
Electromagnetic induction and faraday's
law
Faraday experiments:
Steps:
1- He made a cylinder coil of insulated copper wire such that the coil turns were separated
from each other.
2- He connected the 2 terminals of the coil to a sensitive galvanometer having its zero
reading at the midpoint of its graduated scale.
3- When he plunged a magnet into the coil (Observation) the pointer of the galvanometer
was deflected momentarily in a certain direction 4- When he remove the magnet from the coil (Observation) the pointer of the
galvanometer was deflected in the opposite direction 5- When he fixed the magnet and he moved the coil towards or away from the magnet he
found the same observations
6- When he fixed the magnet inside the coil he found that the pointer of the galvanometer
doesn’t change
Conclusion:
- An electromotive force and an electric current are induced in the coil when the magnet flux
lines cut the coil when the magnet is plunged into or removed from the coil.
1- The magnitude of e.m.f. is direct proportional with the rate by which the conductor cuts
the line of magnetic flux linked with it e. m. f. α ∆φm
∆t
(ɸm is the variation in the magnetic flux intercepted by the conductor in interval ∆t)
- This rate depend on the speed of the magnet and the magnetic flux density
∆ɸm = B .A measured by Weber ( B = magnetic flux density )
2- The magnitude of emf depends on the number of turns of the coil ( N ) which cut the
magnetic flux (emf α N)
𝐞.𝐦. 𝐟. = −𝐍 ∆ɸ𝐦
∆𝐭 …………….. Faraday’s Law
(Volt) or (Weber/sec) or (Tesla.m2 /s)
Faraday Law
Illustrating video
Lenz Rule
𝐞.𝐦. 𝐟. = −𝐍 ∆ɸ𝐦
∆𝐭 …………….. Faraday’s Law
(Volt) or (Weber/sec) or (Tesla.m2 /s)
- This negative sign indicates that the direction of the induced electric current tends to
oppose the cause producing it ( Lenz’s rule )
Illustrating video
Lets Define Things
Faraday’s Law of electromagnetic induction: the induced electromotive force which is
generated in a coil by the electromagnetic induction is direct proportional with the time rate by
which the coil cut (linked with) the lines of magnetic flux and the number of turns of the coil
Lenz’s rule: the induced current must be in a direction such as to oppose the change producing
it.
Solved Example(1)
Solved Example(2)
Illustrating videos