note: this is a brief summary and might contain some errors-plz comment to correct if u find any or for further explanation..
Intro: Faraday and Henry observed that an EMF(electromagnetic force) is produced across the ends of a conductor when the number of magnetic lines of forces associated with the conductor changes. The EMF lasts so long as this change continues. This phenomenon of generating an EMF by changing the number of magnetic lines of forces associated with the conductor is called electro magnetic induction (EMI)
EMF developed is called induced EMF.
if it’s a closed circuit, the current flowing through it is called induced current.
Magnetic flux: number of lines of magnetic induction passing through the area of the coil.
units: Wb (webber)
-Magnetic lines of forces.
-Relative movement of conductor and magnetic lines of forces.
experiment #1: Circular insulated wire of one or more turnes connected to a galvanometer.
i) when a strong magnet is passed through the coil, galvanometer shows deflections indicating current is induced in the coil.
ii) deflections are temporary and lasts as long as the motion between the coil and magnet continues.
iii) more deflections when magnet is moved faster and less when it is moved slowly.
iv) direction of deflection is reversed when same pole of magnet is moved in opposite direction.
experiment #2: two coils are set up with one connected to key and battery, and other to a galvanometer. on opening and closing the key, temporary deflections occur in galvanometer. this is because current is induced in coil 2.
conclusion: the cause of EMF induced in a coil is, change in magnet flux linked with the coil.
the amount of magnetic flux linked with the coil must change in order to produce induced EMF in the coil.
First law: whenever the amount of magnetic flux linked with the circuit changes, an EMF is induced in the circuit. it lasts as long as the vhange in magnet flux continues.
Second law: the magnitude of EMF induced in a circuit is directly proportional to the rate of charge of magnetic flux linked with the circuit.
Strength of induced EMF:
i) rate of change of magnetic field: more rapid the movement and stronger the magnet used, greater is the rate at which the magnetic lines of force cut the conductor and grater the EMI induced.
ii) inductance of the conductor: inductance is the ability of the conductor to have current induced in it. it is constant for any conductor bt high inductance can be designed into a coil by incorporating –
-using many turnes of wire in coil.
– placing the turns closer together.
-winding the coil onto soft iron core.
Lenz’s law: The induced current will appear in such a direction that it opposes the
change force responsible for its production.
Fleming’s right hand rule: according to this rule, if we stretch our fore finger, central finger and thumb such that they are perpendicular to each other then the forefinger represents the direction of magnetic field, thumb represents the direction of motion of conductor and central finger represents the direction of induced current.
P.S: more examples can be used for laws and experiments by the scientists.
p.p.s: i studied this yesterday but did not post it as i was sleepy so did this first thing in the morning.. 😜
1) intermediate second year physics by telugu akademi
2) Clayton’s electrotherapy – 8th edition
3) textbook of electrotherapy by jagmohan singh – 2nd edition