ELECTROMAGNETIC INDUCTION

Electromagnetic Induction Jun 7, 2009

Electromagnetic Induction ,[object Object],Jun 7, 2009 Physics 1 (Garcia) SJSU

Demo : Magnet Induces Current ,[object Object],[object Object],Jun 7, 2009 Physics 1 (Garcia) SJSU Note: Do this in lab too.

Magnetic Recording ,[object Object],[object Object],Jun 7, 2009 Physics 1 (Garcia) SJSU Hard disk

Electric Generator ,[object Object],Jun 7, 2009 Physics 1 (Garcia) SJSU

Demo : Electric Generator ,[object Object],[object Object],Jun 7, 2009 Physics 1 (Garcia) SJSU Magnet Magnet Coils DC Output SHAFT Note: Do this in lab too.

Induction: No Free Lunch ,[object Object],[object Object],Jun 7, 2009 Physics 1 (Garcia) SJSU More difficult to push the magnet into a coil with more loops because the magnetic field of each current loop resists the motion of the magnet.

Faraday’s Law ,[object Object],Jun 7, 2009 Physics 1 (Garcia) SJSU Small Voltage Medium Voltage Large Voltage

Demo : Electromagnetic Oscillations Connect to alternating current (AC) Oscillating Magnetic Field Electro- Magnet Put alternating current into an electromagnet and you create an oscillating magnetic field. This oscillating magnetic field induces electrical currents by inducing electrical field oscillations. This is, effectively, a very low frequency electromagnetic antenna. Coil with bulb

Demo : Electric Motor ,[object Object],Current in Current out Electro-magnets

Electric Motor, Analyzed ,[object Object],[object Object],N S N S Current Current N S N S

Demo : Generator Becomes Motor ,[object Object],Jun 7, 2009 Physics 1 (Garcia) SJSU Rotor Spins Magnet Magnet DC Input Battery Note: Do this in lab too.

Self-Induction ,[object Object],Jun 7, 2009 Physics 1 (Garcia) SJSU Current Primary Magnetic Field Self-Induced Magnetic Field

Demo : Lenz’s Law Jun 7, 2009 Physics 1 (Garcia) SJSU Connect to alternating current (AC) Oscillating Magnetic Field Electro- Magnet Metal ring is levitated by self-induced secondary magnetic field Induced current produces a secondary magnetic field that is always opposed to the primary magnetic field that induced it, an effect called Lenz’s law .

C heck Yourself ,[object Object],[object Object],Jun 7, 2009 Physics 1 (Garcia) SJSU Electro- Magnet

C heck Yourself Jun 7, 2009 Physics 1 (Garcia) SJSU Connect to alternating current (AC) Oscillating Magnetic Field Electro- Magnet Hold the ring down on the shaft and it starts to get hot. Why? What if we cool the ring in liquid nitrogen and repeat the demo?

Demo : Magnetic Brakes Jun 7, 2009 Physics 1 (Garcia) SJSU Strong magnet dropped into a copper pipe falls slowly due to secondary magnetic field induced by its motion. Great America’s Drop Zone has a 22 story freefall, lasting four seconds, decelerated by magnetic braking.

Eddy Currents ,[object Object],[object Object],Jun 7, 2009 Physics 1 (Garcia) SJSU Eddy Currents Primary Magnetic Field Self-Induced Magnetic Field

Metal Detectors ,[object Object],[object Object],[object Object],Jun 7, 2009 Physics 1 (Garcia) SJSU

Demo : Back Electromotive Force ,[object Object],Jun 7, 2009 Physics 1 (Garcia) SJSU When we disconnect a large electromagnet the magnetic field rapidly collapses. This changing magnetic field self-induces a large voltage in the coil of the electromagnet. Large spark occurs at the switch.

ELECTROMAGNETIC INDUCTION

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