H H Magnetic Induction First things First A magnetic field is created around a current-carrying wire. Where do magnetic fields come from? The Possibilities of producing a force a moving charge a current in a wire a moving wire in a magnetic field NDT-Resource Center HyperPhysics Electric Motors and Generators 1) A current flows through the loop of wire immersed in a magnetic field as shown. 2) Each end of the loop of wire will experience a force (right-hand rule) due to the electrons flowing in the loop of wire. 3) The commutator will change the direction of the current every half cycle. 4) Each end of the loop of wire will experience an opposite force due to the electrons flowing in the opposite direction. 5) The loop of wire will continue to rotate due to the changing direction of the current immersed in a magnetic field. Animations: 1, 1b, 2, 2b, 3, 3b, 4, 5, 6 Transformers and Speakers Your CD player has an black adapter on the end of the power supply cord. It requires 9-12 volts, not 120 volts. So, the transformer inside the black box steps-down the voltage. The current, alternating at the same frequency as the sound waves that generated it, induces an alternating magnetic field in the coil. As the polarity of the magnetic field of the coil alternates, it is alternatively attracted to and repelled by the permanent magnet. This causes the coil to vibrate. The vibrating coil causes the attached cone shaped diaphragm to vibrate and reproduce the sounds generated by the original source. Thomson Ring This will change your minds about physics! Magnetic Memory Magnetic Domains are represented by the arrows NDT-Resource Center Basic Physical Principles Reading a Magnetic Tape Hyperphysics 1) The signal comes from the the Magnetic Tape. 2) Each Strip on the magnetic tape is polarized in either a N-S or S-N orientation. 3) These magnetic orientations represented either a one or a zero (digital). 4) As the Magnetic tape passes, an induced magnetic field is established in the Iron core. 5) This induced magnetic field in the Iron core changes according to the signal coming from the magnetic tape. 6) The changing induced magnetic field will create a changing current (voltage) in the coil. 7) This changing current (voltage) is fed to the amplifier circuit. Writing to a Magnetic Tape How much information can we get on a magnetic tape? Evolution of Technological Memory You know those CD-Rs that you've trusted your most precious memories to? They could be little more use than coasters after just two years. Michael Pollitt investigates The Independent The Evolution of a good idea Magneto-Optical Storage Storage Limits On Our Visual Hard Drive NASHVILLE, Tenn. -- Scientists have discovered the region of the brain responsible for the old adage, "out of sight, out of mind."     The amount of information we can remember from a visual scene is extremely limited and the source of that limit may lie in the posterior parietal cortex, a region of the brain involved in visual short-term memory, Vanderbilt psychologist René Marois and graduate student J. Jay Todd have found. Their results were published in the April 15 edition of Nature. (more) Holographic Memory What is a Hologram? making a hologram Light Interference I,II Laser Light is coherent and monochromatic. Hyperphysics Information Storage is 3-dimensional information is stored in every part of the hologram! A cube of Lithium Niobate Optical Memory Holographic Information Storage Technology I, II Bacteriorhodopsin Molecular Memory