* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download 7TH CLASSES PHYSICS DAILY PLAN
Magnetosphere of Jupiter wikipedia , lookup
Maxwell's equations wikipedia , lookup
Geomagnetic storm wikipedia , lookup
Magnetosphere of Saturn wikipedia , lookup
Edward Sabine wikipedia , lookup
Electromagnetism wikipedia , lookup
Magnetic stripe card wikipedia , lookup
Friction-plate electromagnetic couplings wikipedia , lookup
Mathematical descriptions of the electromagnetic field wikipedia , lookup
Neutron magnetic moment wikipedia , lookup
Lorentz force wikipedia , lookup
Magnetic monopole wikipedia , lookup
Magnetic nanoparticles wikipedia , lookup
Giant magnetoresistance wikipedia , lookup
Magnetometer wikipedia , lookup
Magnetic field wikipedia , lookup
Electromagnetic field wikipedia , lookup
Multiferroics wikipedia , lookup
Earth's magnetic field wikipedia , lookup
Magnetotactic bacteria wikipedia , lookup
Magnetotellurics wikipedia , lookup
Magnetohydrodynamics wikipedia , lookup
Magnetoreception wikipedia , lookup
Magnetochemistry wikipedia , lookup
Electromagnet wikipedia , lookup
Faraday paradox wikipedia , lookup
Eddy current wikipedia , lookup
Superconducting magnet wikipedia , lookup
Ferromagnetism wikipedia , lookup
10TH CLASSES PHYSICS DAILY PLAN SUBJECT: M MA AG GN NEETTIISSM M AIM:To learn the properties of the magnets DURATION: 120 min REAL LIFE:Magnets PRESENTATION: M Maaggnneettiicc pprrooppeerrttiieess:: A magnet is an object that has the property of attracting magnetic substance. Substances, which are attracted by a magnet, are called magnetic, and those, which are not attracted by a magnet, are called nonmagnetic. For ex: Iron, Cobalt, Nickel are magnetic but Aluminum is a nonmagnetic material. (SHOW!). If you have a magnetic material you can create an artificial magnet by rubbing it with another magnet.(SHOW!). In nature a magnet is an iron oxide (magnetite) but we can produce artificial magnets in different sizes and shapes, such as bar magnet, U shaped magnet horse-shoe magnet round magnet, etc…FIGURES M Maaggnneettiicc ppoolleess:: If a bar magnet is dipped into iron filings, it holds filings in large amount near its two ends (SHOW) This shows that, the forces, which make the fillings collect, are concentrated mainly near the ends. These two ends are called poles of magnet. Poles are always found in pairs. In another words a magnet has two poles (north and south) and there is no magnet having only one pole. Two poles have exactly the same strength of attraction. field lines and the force acting S pole is in the opposite direction of the field lines. M Maaggnneettiicc FFiieelldd,, FFiieelldd IInntteennssiittyy,, FFiieelldd LLiinneess When iron filings are scattered on a sheet of plastic above a bar magnet become aligned in certain directions. The lines around the magnet are called magnetic field lines. The number of magnetic field lines passing through a unit surface is called magnetic field strength or magnetic flux density or magnetic inductor. N N S S N S N N 3) Magnetic Field Vector (B): B vector is always tangent to field lines. Magnitude of the vector at a point shows strength of field. B B Bar magnet When a bar magnet is suspended or pivoted so that it can turn freely about a vertical axis in a horizontal plane, it turns and omes to rest approximately north- south direction. For this reason, the end of magnet that points north is called its north pole (N), and the other end is called its south pole (S). N S Bar magnet N S N S N S B B Therefore: If field line is circular, B vector is perpendicular to radius. Unit: Unit of B is Tesla (T), or Weber m 2 (Wb/m2) Wb (SI system) m2 Method of Producing Magnets We can make artificial magnets since natural ones are not easy to find. to do this, we stroke one pole of a bar a) by stroking: magnet along in a iron bar several times in the same direction then, iron Ñ bar becomes magnet. 1T=1 N S N S U magnet Like poles (N-N), (S-S) repel each other and opposite poles attract each other. A compass needle is also a bar magnet and shows (NS) directions. M Maaggnneettiicc FFiieelldd:: ((BB)) If a bar magnet is brought near another magnet, they apply a force on one another. The region about a magnet where its influence is understood or shown is called ``magnetic field of that magnet``. Magnetic field lines are directed away from on N pole and towards on S pole. Where the magnetic field lines are close together the field is strong and where they separated, the field is weak. At the two poles, field is the strongest. When you change the location of a test compass around a bar magnet, at any point needle of compass will show a particular direction and these shows magnetic field around a magnet is variable and has a direction. If a compass needle is located in a uniform magnetic field, the force acting N-pole is in the direction of magnetic b) by contact: If either N or S pole of a magnet comes into contact with an iron nail then, nail becomes magnet. N S c) by induction: N S If iron nail is brought near to a magnet, because the magnetic field of an iron bar affect the nails, nail becomes a magnet for a while and can attract iron filings. . . Iron filings 1 d) By the means of earth’s magnetic field If you place an iron bar at an angle with the horizontal and strike bar with a hammer several times. Then the iron bar becomes a magnet. Because, sudden motions of the domains in the iron bar are aligned in the direction in the earth’s magnetic field PPrroodduucciinngg EElleeccttrroo m maaggnneett By using electric current we will produce some effect of a magnet. When electric current passes through a conducting wire produces circular magnetic field lines around the conductor. When you pass this electric current through a coil, an intense magnetic field is formed. And when you enter an iron bar into the coil, the bar becomes electromagnet. 1.Diamagnetics: if Mr less than unity (meanly Mr=0,999982) (for lead). They make the field a little weaker. 2.Paramagnetics: If Mr is slightly greater than unity (1,000022) for Aluminum. They make the field a little stronger. 3.Ferromagnetic materials: If Mr>>1 much larger than unity (100,1000,…)(iron, cobalt, nickel). They make the field much stronger. The Magnetic Field of the Earth N The earth is a giant magnet itself. The geographical pole and magnetic pole are not at the same place. 2100 km S N M Maaggnneettiicc FFlluuxx ((O O)) Magnetic flux is the total number of magnetic field lines passing thruogh a certain cross-sectional area. S Declination angle is between geographical and magnetic north. Inclination angle is between the magnet needle and horizontal. [Inclination angle is zero only at the magnetic equator] B A Magnetic filed of earth is about 10-5 T. B if the chosen surface is not perpendicular to the line then: N We define normal to the surface α O=BAcos α α is the angle between normal to the surface and the magnetic field lines. ex1: The uniform magnetic field in a certain region has a magnitude of 2T, and its direction is horizontal. The plane of a rectangular coil 20cm by 30cm makes an angle of 37 0 with the field. Compute the flux, O, through the coil. Solution: A=20.30=6.10-2.m2 O=BA.cos α=6.10-2.2cos 530 O= 0,072 wb Magnetic Permeability (μ) It is a characteristic property of a substances and a measure of ability to increase or decrease the value of B in the region. Suppose that the uniform magnetic field at a certain point in vacuum is Bo. if a piece of iron is placed in the region, the field at that point will change to a new value B. The relative permeability μb of the material is given as μb=magnetic field in material / magnetic field in vacuum in symbols, μb=B/Bo We can also write the formula between permeability’s as follows μb= μ / μo =oermeability of material/permeability of vacuum.For vacuum, permeability μo =4П.10-4wb/AM Relative permeable of vacuum is 1. (and also air) Shortly, magnetic permeability of a substance is the ability to increase or decrease the value of B in the region. HOMEWORK: MULTIMEDIA: electromagnetism, akademedia DEMONSTRATION: magnets, field lines EXPERIMENT: TEACHER: DIRECTOR: We can classify substances into three groups according to their relative magnetic permeabilities. 2