1 / 24

ELECTRICITY AND MAGNETISM

ELECTRICITY AND MAGNETISM. ELECTRICITY.

tolla
Télécharger la présentation

ELECTRICITY AND MAGNETISM

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ELECTRICITY AND MAGNETISM

  2. ELECTRICITY • Is a basic feature of matter that makes up everything in the universe. When most people hear electricity, they think of lights, television, microwave ovens, computers, air conditioners, and other electrically powered devices. Electricity makes these and many other useful things possible. But electricity is much more important than that.

  3. Electricity and magnetism together make up a force called electromagnetism, one of the fundamental force of the universe. Electrical force is responsible or holding together the atoms and molecules from which matter is composed. In this way, electricity determines the structure of every object that exists.

  4. Electricity is also associated with many biological processes. In the human body, electrical signals travel along the nerves, carrying information to and from the brain. Electrical signals tell the brain what the eyes see, what the ears hear and what the fingers feel. Electrical signals from the brain tell muscles to move. Electrical signals even tell the heart when to beat.

  5. Electricity and electron comes from the greek word “elektron” (the former greek work for amber). • Lodestone or magnetite- black rock (also attract things).

  6. Kinds of Electricity Static Electricity Static Electricity is caused when particles of opposite charge get separated. The two kinds of particles are attracted to each other. When the attraction becomes strong enough, the particles quickly stream back together.

  7. Kinds of Electricity • Electric Current • An electric current is the flow of electrons through a material. Materials that carry a current are called conductors. Metals are the conductors, so electrical wires are made of metal. Most wires that are used to carry electric current are made of copper. • Materials that do not conduct electricity are called insulators. Rubber and plastic are both good insulators. Most electrical wires are rapped in rubber. The rubber prevents shocks. • An electric current needs a complete path in which to move. This path is called a circuit. If a circuit is broken, the current also stops flowing.

  8. Kinds Of Electric Current • Direct Current / DC - the electrons always move in the same direction • Alternating Current / AC (wall outlets) - the electrons in the circuit move rapidly back and forth

  9. Magnetism • Magnetism comes from the electron in atoms. Electrons spin like little tops. And every electron has an invisible area of magnetism around it. This area is called the magnetic field. In some metals, the spinning electrons turn each atom into a tiny magnet. Those atoms can be made into line up in the same direction. Then the entire piece of the metal becomes magnetic. Most magnets are made of iron.

  10. Static electricity

  11. Static Electricity • Electrons are displaced WITHOUT moving througha conductor e- displaced & builds charge(not moving through a conductor) Eventually electrons “jump” to a positively charged object Examples • Plastic sheet & hair • Walking on carpet & • Touching a metal doorknob

  12. Moving magnet can generate electricity. • Electric currents cause magnetism.

  13. Law of Charges • All like charges repel ( push away from ) each other • All unlike charges attract ( pull towards ) each other • Static electricity is an imbalance of electric charges within or on the surface of a material. The charge remains until it is able to move away by means of an electric current or electrical discharge. Static electricity is named in contrast with current electricity, which flows through wires or other conductors and transmits energy

  14. Coulomb’s Law Fe = k q1q2 r2 Where: Fe = is the electric force in Newtons (N) k = is a constant equal to 8.99 x 109 Nm2/C2 q1 and q2 = are charges in Coulombs ( C ) r = is the center-to-center distance between the charges in meters

  15. Example • A positive charge of 6.0 x 10 -6C is 0.030m from a second positive charge of 3.0 x 10 -6C. Calculate the force between the charges. Fe = k q1 q2 r2 = (8.99 x 109 N m2/C2 ) (6.0 x 10 -6C) (3.0 x 10 -6C) ( 0.030m )2 =(8.99 x 109 N m2/C2 ) (18.0 x 10 -12C) (9.0 x 10 -4 m2) = + 1.8 x 10 -8 N

  16. MAGNETIC FIELDS An area where the force exists; area where force is felt Magnetic field lines • Leaves north pole & enters south pole • Lines closer together = stronger field NOTICE • Strongest at the poles • Field lines start at the NORTH pole and travel towards the SOUTH pole

  17. We used g= force/mass to measure the gravitational field and E= force/charge to measure the electrostatic field. • Finding the strength of magnetic field Eqn: B= F/p • Where: F = is the force in newtons p = is the pole strength in ampere- meters B = is the magnetic induction in newtons/ampere-meter

  18. Example At a certain point in a magnetic field, a 2-ampere-meter test pole has a maximum force of 10 newtons south exerted upon it. What is the strength and the direction of the magnetic field at this point? B= F/p = 10 N south/ 2 ampere-meters = 5 N/ ampere-meter, south

  19. Flux lines (called webers) • Finding the magnitude of magnetic field Eqn: B= Φ A • Where: B and A are perpendicular Φ = flux in webers A = area in meters2 B = is the magnetic induction in webers/meters2 and is the magnitude of the field-meter

  20. Example At a certain point in a magnetic field, there are 100 webers per 5 meters2 of area. What is the magnitude of the field? B= Φ A = 100 Wb/ 5m2 = 20 Wb/m2 = 20 N/ampere-meter

  21. Electromagnetism If you take a soft iron nail, wrap a several turns of insulated wire on it, connect it on a battery, you will find that the iron nail exhibits the properties of a permanent magnet as long as charge flows in the wire. What most people do not realize is that if the nail is withdrawn from the coil, the coil still behaves in every way like permanent magnet, but with weaker magnetic properties.

  22. The Magnetic Force on a Moving Charge • Whenever a moving electric charge enters an external magnetic field, the magnetic field associated with the charge interacts with the external field. This results in a magnetic force that tends to push the charge in sideways. • Using a Right Hand Screw Rule, point your thumb in the direction of the velocity of the moving charge. Since velocity and magnetic field are perpendicular with each other, the thumb points to the direction of the charge, and the direction of the magnetic field is through your fingers.

  23. F= Bqv • Where: F is the magnitude of the force in newtons B is the magnetic induction in webers/meters2 Q v

More Related