Electromagnetic FieldBy

T.Jayachandran/ECENandha Engineering College

Forces • A force is a push or pull upon an object resulting from the object's interaction

with another object. Whenever there is an interaction between two objects, there is a force upon each of the objects.

• Gravitational Force (center of gravity)• Electrical Force• Magnetic Force

Others• Applied Force• Normal Force• Frictional Force• Air Resistance Force• Tension Force• Spring Force

Newton’s Laws

• First law • Second law • Third law

Newton’s First law

• All object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force. This law is often called "the law of inertia".

Example

Newton’s second law

• Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object).

F=M*A or 

FORCE = MASS times ACCELERATION

Newton’s Third law

•  For every action there is an equal and opposite re-action.

        

Electromagnetic Field

• Electric + Magnetic + Field

Magnetic Field

Attraction and Repulsion

Magnetic field and Magnetic Intensity

• Magnetic field - A magnetic field is the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude (or strength); as such it is a vector field.

• Magnetic field intensity – Magnetic field strength

Electric field

• Electric field is defined as the electric force per unit charge. The direction of the field is taken to be the direction of the force it would exert on a positive test charge. The electric field is radially outward from a positive charge and radially in toward a negative point charge.

• Electric field intensity- strength

• Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. There are two types of electric charges:

Positive and negative.

Electromagnetic field• An electromagnetic field (also EMF or EM field) is a

physical field produced by electrically charged objects. It affects the behavior of charged objects in the vicinity of the field.

ElectromagnetismFaradays Law on Induction• FIRST LAW of Faraday's Electromagnetic Induction state that

whenever a conductor are placed in a varying magnetic field emf are induced which is called induced emf, if the conductor circuit are closed current are also induced which is called induced current.

• Second Law of Faraday's Electromagnetic Induction state that the induced emf is equal to the rate of change of flux linkages (flux linkages is the product of turns, n of the coil and the flux associated with it).

Two laws

• Law 1- Motor • Law 2 - Generator

Applications of EMF

• Motor • Generator• Cycle dynamo• Mutual inductance• Self inductance• Transformers• Eddy currents• Magnetic Recording

Applications• RF communication• Microwave Engineering• Antennas• Electrical Machines• Satellite Communication• Atomic and nuclear research• Radar Technology• Remote sensing• EMI EMC• Quantum Electronics• VLSI

Electrostatics • Static electricity is an imbalance of electriccharges within or

on the surface of a material. Thecharge remains until it is able to move away by means of an electric current or electrical discharge

Demo

Applications of Static electricity

• Laser Printers• Xerography• Laser Printers• Ink Jet Printers and Electrostatic Painting

• Electrostatics in everyday life • Question: Describe briefly two applications of electrostatic phenomenon in everyday life.• • Answer:• When you take off a pullover over a nylon shirt there is a crackling sound• A pen rubbed with a piece of cloth will pick up small pieces of paper • A television screen easily collects dust• You sometimes get a small electric shock when getting out of a car• If you roll over in bed you can sometimes see small flashes of light between the sheets• You can sometimes get a small electric shock from a cat that has rolled on a synthetic carpet• In a thunder storm there are huge flashes of lightning• Book covering film can be difficult to work with• • Other detailed applications• 1. A charged mesh in a chimney acts as an electrostatic dust collector, cleaning the smoke.• 2. Paint sprays can be charged and the object they are spraying earthed to attract the paint towards it.• 3. Vinyl records have to be cleaned to remove the static charge that builds upon their surface.• 4. People thought that static electricity was the cause of car sickness until it was remembered that a static charge can only be on the

outside of a hollow conductor like a car.• 5. Photocopiers work by a charged sheet attracting fine carbon powder to make the image• 6. It can be shown that a water molecule is polar - that is it has one positive end and one negative one. A stream of water can be

deflected by a charged polythene rod placed nearby• 7. Capacitors• A capacitor stores static charge - in its simplest form it is two plates that are separated by air. More charge can be stored by increasing

the area of the plates, putting them closer together or using another insulator instead of air. In a practical capacitor the plates are usually rolled up with paper insulation in between them. In a radio receiver a variable capacitor with moveable plates is used as the tuner.

• 8. People must take care when emptying oil tankers and refuelling aircraft to avoid a build up of static charge due to friction that could make a spark and result in an explosion.

• 9. Problems and uses of cling film• 10. Sellotape sticking to everything except what you want it to when you pull it off the roll