www.BZUpages.com

Magnetic Field

Presented to Sir Tariq bhatiBy M.Aatif Aneeq

0715

www.BZUpages.com

Magnet

Observation of the magnetic properties of the mineral magnetite (Fe3O4) or Lodestone ( A

lodestone is a form of magnetite which demonstrates distinctive magnetic qualities.)

probably began several thousand years ago when early Greeks found naturally occurring magnets

attracted small pieces of iron.They people use magnet as compass needle about

1000 A.DChinese may have known about the north south

effect of a magnet much earlier.Magnet was found near the city of Magnesia.

www.BZUpages.com

Magnetic force/field

Electric force F=qE on the charge q produced within the electric field E.Similarly for studying magnet we consider magnetic field B.Magnetic field is the vector field which exert force on the moving charges.

www.BZUpages.com

Magnetic force/fieldWe take an example of Cathode Ray Tube. In which small magnet deflect the electron beam in cathode ray tube.

www.BZUpages.com

Magnetic force/field

Demonstrate electron beam deflection by a magnetic field as a moving spot on the screen.

www.BZUpages.com

Magnetic force/field

The deflecting force is always perpendicular to the velocity of the moving electrons.

www.BZUpages.com

Magnetic force/fieldThe Magnetic field B is the vector field that exerts a force F on the charged particles

F = qv x B

Magnetic force to be exerted on a particle

•Must be Charged•Must be Moving

www.BZUpages.com

Magnetic force/field

Direction of force by Right Hand Rule

www.BZUpages.com

Magnetic force/field

F = | qvB sinθ |

www.BZUpages.com

Magnetic force/fieldF = | qvB sinθ |

Where Sinθ = 90 = 1

Hence force F = qvB

The SI Unit of the Magnetic Field is (N/C) / (m/s)

Which is called tesla. T. Tesla is the large unit of Magnetic field.

www.BZUpages.com

Magnetic force/field

As we know Force exerted on charge is Always perpendicular to the Velocity “V” ButWork done by this force is zero…

We know thatW= F.S

Work done in a small region dɭ will bedW=F. dɭ

As v = dɭ/dtdɭ = vdt

www.BZUpages.com

Magnetic force/fielddW= F. Vdt

Since θ between F and V is 90 So cos 90 = 0

Therefore Work “W“ done by magnetic force is zero

Iron Filing Aligns with the field of a bar magnet