24_Magnetic_Fields_and_Forces

24_Magnetic_Fields_and_Forces - Circuits revision Heres the...

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1 Circuits revision • Here’s the circuit for the flashing neon bulb. • What is the period of the flash in seconds ?
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2 Magnetic Fields revision Please try problem 15 in Ch 24 on page 825. “What is the magnetic field at the center of the loop….”
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3 Magnetic Fields and Forces Magnetism Magnetic field shapes and direction Fields near electric currents Magnetic forces Moving charges and magnetism Magnetic machines Magnetic materials
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4 Magnetism • Fundamental force of nature • Related to electricity, but not the same
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5 Experimental Observations • Magnetism does not move an electroscope, it does not act on stationary charges • Long range force (action over a distance) • There are 2 poles, north and south , and they come in pairs • Like poles repel, unlike poles attract • Poles attract magnetic materials
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6 Magnetic Field lines • Magnetic Fields around a bar magnet • Similar to an electric dipole • Start at north pole, terminate at south pole
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7 Like and unlike poles Magnetic field lines between poles
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8 Electric Currents and Magnetic Fields Oersted found that a current can move a magnetic compass
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9 Direction of Magnetic field We use the right handed rule to find which way a magnetic compass would point
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10 Magnetic field near a loop • Bend the wire into a loop. • Dots - field is coming out of the page. • Crosses - field is going in to the page
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11 Field near a solenoid • Many loops will concentrate the field inside the coil • Called a solenoid – contains a uniform magnetic field
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Magnetic field due to a current Experimentally, the field strength, B, is proportional to current, I, and inversely proportional to distance, r. Units of Tesla, where μ
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This note was uploaded on 12/28/2011 for the course PHYSICS 122 taught by Professor Bhagat during the Fall '11 term at Maryland.

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24_Magnetic_Fields_and_Forces - Circuits revision Heres the...

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