Magnetic Field Presented to Sir Tariq bhati By M.Aatif Aneeq 0715

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.D Chinese may have known about the north south effect of a magnet much earlier. Magnet was found near the city of Magnesia.

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.

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

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

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

Magnetic force/field The 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

Magnetic force/field Direction of force by Right Hand Rule

Magnetic force/field F = | qvB sinθ |

Magnetic force/field F = | qvB sinθ | Where Sin θ = 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.

Magnetic force/field As we know Force exerted on charge is Always perpendicular to the Velocity “V” But Work done by this force is zero… We know that W= F.S Work done in a small region d ɭ will be dW=F. d ɭ As v = d ɭ /dt d ɭ = vdt

Magnetic force/field dW= F. V dt 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