Magnetic Fields By: Engr. Hinesh Kumar Lecturer I.B.T, LUMHS

Magnetism Since ancient times, certain materials, called magnets, have been known to have the property of attracting tiny pieces of metal. This attractive property is called magnetism. N S Bar Magnet N S

Magnetic Poles The strength of a magnet is concentrated at the ends, called north and south “poles” of the magnet. A suspended magnet: N-seeking end and S-seeking end are N and S poles. NS N E W S N Compass Bar magnet S N Iron filings

Magnetism is the force of ___________ or ___________ of magnetic materials. attractionrepulsion Magnetic Attraction-Repulsion

N S N N S S NS NS Magnetic Forces: Like Poles Repel Unlike Poles Attract

Magnetic Field A field of force surrounding a permanent magnet or a moving charged particle, in which another permanent magnet or moving charge experiences a forceA field of force surrounding a permanent magnet or a moving charged particle, in which another permanent magnet or moving charge experiences a force The lines of force surrounding a permanent magnet or a moving charged particle.The lines of force surrounding a permanent magnet or a moving charged particle. Its a vector quantity.Its a vector quantity. Its units: Tesla, GaussIts units: Tesla, Gauss

A __________ ______ is an area around a magnet that applies a force to magnetic materials without touching them. Magnetic Field magnetic field

The magnetic field actually keeps going out forever, it just gets weaker the farther away from the magnet it is. It eventually gets too weak to move anything.

Magnetic Field Lines NS We can describe magnetic field lines by imagining a tiny compass placed at nearby points. The direction of the magnetic field B at any point is the same as the direction indicated by this compass. Field B is strong where lines are dense and weak where lines are sparse.

Properties Magnetic field lines are continuous and unbroken, forming closed loops.Magnetic field lines are continuous and unbroken, forming closed loops. A magnetic field line can never cross another field lineA magnetic field line can never cross another field line Magnetic field lines are defined to begin on the north pole of a magnet and terminate on the south pole.Magnetic field lines are defined to begin on the north pole of a magnet and terminate on the south pole. If magnetic monopoles existed, then magnetic field lines would begin and end on them.If magnetic monopoles existed, then magnetic field lines would begin and end on them.

Field Lines Between Magnets NS NN Unlike poles Like poles Leave N and enter S Attraction Repulsion

Electromagnets Electromagnets An electromagnet is formed when a ________ in an electric circuit is wrapped around an _____ _____ producing a magnetic field.An electromagnet is formed when a ________ in an electric circuit is wrapped around an _____ _____ producing a magnetic field. The magnet that results loses its magnetism if the electric current ______ ________.The magnet that results loses its magnetism if the electric current ______ ________. Electric current is simply the flow of ______________.Electric current is simply the flow of ______________. (or the flow of charged particles, like electrons) wire iron core stops flowing electricity

Generators Generators ____________ ___________.A generator changes ____________ energy into ___________ energy when a coil of wire is rotated near a magnet. mechanicalelectrical N S

Simple Electric Motors A motor changes ___________ energy into ____________ energy by rotating an electromagnet between _______ of a magnet. electrical mechanical poles N S

How it works : The coil of the electromagnet is connected to a source of ___________.The coil of the electromagnet is connected to a source of ___________. When electricity flows through the electromagnet, a ___________ field is produced.When electricity flows through the electromagnet, a ___________ field is produced. electricity magnetic S N N S

N S The rotating coil of wire can be _________ to an object to make it _____.The rotating coil of wire can be _________ to an object to make it _____. Examples: ________ on an electric car, ___ blades, a ______ ____. attachedspin wheelsfan

N S The rotating coil of wire can be _________ to an object to make it _____.The rotating coil of wire can be _________ to an object to make it _____. Examples: ________ on an electric car, ___ blades, a ______ ____. attachedspin wheelsfan disco ball But, what good is a disco ball without lights or music?