* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Diapositiva 1
Magnetosphere of Saturn wikipedia , lookup
Friction-plate electromagnetic couplings wikipedia , lookup
Edward Sabine wikipedia , lookup
Geomagnetic storm wikipedia , lookup
Electromotive force wikipedia , lookup
Skin effect wikipedia , lookup
Magnetic stripe card wikipedia , lookup
Maxwell's equations wikipedia , lookup
Neutron magnetic moment wikipedia , lookup
Giant magnetoresistance wikipedia , lookup
Magnetometer wikipedia , lookup
Mathematical descriptions of the electromagnetic field wikipedia , lookup
Magnetic monopole wikipedia , lookup
Earth's magnetic field wikipedia , lookup
Electric machine wikipedia , lookup
Magnetotactic bacteria wikipedia , lookup
History of electrochemistry wikipedia , lookup
Electricity wikipedia , lookup
Electromagnetism wikipedia , lookup
Electromagnetic field wikipedia , lookup
Lorentz force wikipedia , lookup
Magnetoreception wikipedia , lookup
Magnetohydrodynamics wikipedia , lookup
Superconducting magnet wikipedia , lookup
Magnetotellurics wikipedia , lookup
Magnetochemistry wikipedia , lookup
Multiferroics wikipedia , lookup
Eddy current wikipedia , lookup
Electromagnet wikipedia , lookup
Ferromagnetism wikipedia , lookup
Magnetic field Compass Needle Vocabolario: Compass needle: ago della bussola True North: Polo nord geografico Circuit, Loop: circuito (elettrico) Magnet: magnete Iron filings: limatura di ferro Wire carrying an electric current: filo percorso da corrente elettrica Magnetic permeability: permeabilità magnetica To point: indicare To exercise: esercitare Magnets are objects able to attract metallic materials (items made of iron or steel). Magnets also attract each other but only if they are properly aligned. (If the ends are not properly aligned the force between them is repulsive rather than attractive). They show a similarity with an electric dipole behaviour: each magnet has two poles, (usually labelled with the letter N and S) and, as for electric charges, like poles repel each other while unlike pole attract one another. Magnetic poles The magnetic field produced around a magnet can be easily detected by sprinkling iron filings near it: the filings line up in the direction of the magnetic field produced, revealing the field lines in the neighbourhood of the magnet . iron filings Compass Needle As we can see in the figure below, the magnetic field produced by a magnet has similar pattern to the electric field lines produced by an electric dipole. The main difference is that the magnetic field lines are closed loop (they have no origin and no ending point) while electric field lines always originate from positive charges and end on negative charges. True North North magnetic pole South Magnetic pole True South Hans Christian Oersted (1777-1851) was a Danish physicist and chemist 100 danske kroner − Danish banknote from 1970 featuring Ørsted Ørsted developed an experiment which provided evidence that surprised him. As he was setting up his materials, he noticed a compass needle deflected from magnetic north when the electric current from the battery he was using was switched on and off. This deflection convinced him that magnetic fields radiate from all sides of a wire carrying an electric current, just as light and heat do, and that it confirmed a direct relationship between electricity and magnetism. Oersted’s experiment Wire carrying an electric current Oersted demonstrated that a current produces a magnetic field Magnetic field wire carrying an electric current Michael Faraday,(1791 – 1867) was an English chemist and physicist magnetic forces are exerted by magnets on current carrying wires André-Marie Ampère (1775 –1836), was a French physicist. The SI unit of measurement of electric current, the ampère, is named after him. Ampere discovered the existence of force exerted on one current-carrying wire by another. Ampere measured the strength of this magnetic force and studied how it varies with the distance between the wires and the amount of current flowing in each. He showed that the magnetic force between the wires is proportional to the two currents i1 and i2 and inversely proportional to the distance r between the two wires. 0 i1i2l F 2 r 0 i1i2l F 2 r μ0 = magnetic permeability [ μ0 = 4π × 10-7 N/A2 ] l = lenght of the wire If the currents in the wires have the same direction, the resulting force is attractive; if the currents have an opposite direction, the resulting force between the wires is repulsive.