### ELECTRO MAGNETISM

* The leading scientist of 19th century Hans Christian Oersted played a crucial role in understanding electromagnetism.
* In 1820, he discovered that a compass needle got deflected when a metallic conductor carrying current is placed near by it.
* Any change in direction of current will show variation in deflection. Thus Electricity and Magnetism are related phenomena.
* The region surrounding a magnet in which its effect can be experienced i.e. its force can be detected is called magnetic field.
* The imaginary lines representing magnetic field around a magnet are called as field lines or field lines of magnet.
* The magnetic lines of force originate from north pole of a magnet and end at its south pole.
A magnetic field line is a closed and continuous curve.
* The magnetic field lines never intersect each other.

* The number of magnetic lines of force crossing through the surface normally is defined as magnetic flux. It is denoted with Where 'B' is the magnetic field induction.
'A' is the area of cross section.
* The units of magnetic flux in S.I. System are Webers (Wb).
* The number of lines of induction passing normally through unit area is called flux density (or) Magnetic induction and it is denoted by 'B'. * S.I. Unit of magnetic induction is Weber / meter2 (or) Tesla.
* Current carrying wire produces magnetic field.
* There are two methods recognise the direction of the magnetic field due to a current flow is a conductor
Maxwell's Cork - Screw law: It states, if the current in a conductor is in the direction of a tip of the screw then the direction of the magnetic flux is in its head moment direction.

Ampere's right hand rule: If the direction of current is a conductor is in our right hand thumb way then the magnetic field due to current flow is in the direction in which our fingers curl around the wire.
Solenoid:
i) A long wire wound in a close packed helix is called as solenoid.
ii) A solenoid works as a bar magnet when current passes through it.
iii) The magnetic field formal when current passed through a solenoid is just like the filed of a bar magnet.
iv) The magnetic lines of force move from north to south of the out side of a solenoid.
v) Where as the magnetic field lines of force more from south to north in the inner side of a solenoid.
A particle having a charge 'q' is moving with a speed of 'v' is a magnetic field 'B' making an angle θ with the field then the force experienced by the particle. * Fleming left hand rule: Stretch the fore finger, middle finger and thumb of a left hand mutually perpendicular to each other, then the current in the conductor consider in the direction of middle finger and the direction of the magnetic field along fore finger then the force on the current carrying conductor is in the direction of thumb.
* Electric motor : It is one which converts electrical energy into a mechanical energy.
* Parts of the motor are
i) Armature
ii) A permanent magnet
iii) Commutator
iv) Carbon brushes
v) Source
* Speed of motor depends on number of turns in the coil (n), electric current passing through the coil (c) and area of the armature (a) and depends on magnetic field induction 'B'.
* The phenomenon of generation of an electric current in a closed circuit from magnetic effects i.e., by changing the magnetic field is called electromagnetic induction.
* Electric current produced due to this phenomenon is called induced current.
* Induced EMF = change in flux / time * Lenz's law: The induced current set up in the coil is in such a direction that it opposes the changes in the flux.
Applications of Faraday's law of electromagnetic induction:
(i) Check gates that are arranged at important places.
(ii) Recording and reproducing of sounds on tape recorders.
(iii) To read magnetic strip when we swipe our ATM card.
(iv) In preparation of inductive stove.
(v) Faraday's laws are more useful in production and transmission of electricity and also we are applying these laws in AC. generator, electric motors, self induction, mutual induction, and transformers.
* In generators, mechanical energy is converted into electrical energy.
* Two kinds of generators are there:
(i) A.C. generators
(ii) D.C. generators

AC means alternating current: The direction of the current changes in regular time intervals. To get this A.C we arrange two slip-rings permanently to the ends of the coil. A.C. generator works on the principle of Faraday's electromagnetic induction.
Main parts in a A.C. generators:
(i) Horse-shoe magnet to keep a regular magnetic field.
(ii) A rectangular armature
(iii) Two slip rings
(iv) Two carbon brushes
* It generates the current which does not changes its direction with time. i.e., unidirectional
current called Direct Current. The direction of current in external circuit remains the same.
* D.C. generator works on the principle of Faraday's electromagnetic induction.
* This device two half-slip rings arranged at the ends of the coil. As they touch one after one. We get the current in single direction.

Conceptual flow chart: Posted Date : 18-11-2020

గమనిక : ప్రతిభ.ఈనాడు.నెట్‌లో కనిపించే వ్యాపార ప్రకటనలు వివిధ దేశాల్లోని వ్యాపారులు, సంస్థల నుంచి వస్తాయి. మరి కొన్ని ప్రకటనలు పాఠకుల అభిరుచి మేరకు కృత్రిమ మేధస్సు సాంకేతికత సాయంతో ప్రదర్శితమవుతుంటాయి. ఆ ప్రకటనల్లోని ఉత్పత్తులను లేదా సేవలను పాఠకులు స్వయంగా విచారించుకొని, జాగ్రత్తగా పరిశీలించి కొనుక్కోవాలి లేదా వినియోగించుకోవాలి. వాటి నాణ్యత లేదా లోపాలతో ఈనాడు యాజమాన్యానికి ఎలాంటి సంబంధం లేదు. ఈ విషయంలో ఉత్తర ప్రత్యుత్తరాలకు, ఈ-మెయిల్స్ కి, ఇంకా ఇతర రూపాల్లో సమాచార మార్పిడికి తావు లేదు. ఫిర్యాదులు స్వీకరించడం కుదరదు. పాఠకులు గమనించి, సహకరించాలని మనవి.