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AT HOME*

AT HOME*. VIDEO. AT SUPERMARKET*. Eternity Flashlight. Invented by…. Pat Y Mah Daka Designs Ltd. Hong Kong. Advantages No Batteries, no bulbs, Environmentally-friendly Super Bright LED (Light Emitting Diode) Only 30 seconds of shaking gives 5 minutes of light

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AT HOME*

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  1. AT HOME*

  2. VIDEO

  3. AT SUPERMARKET*

  4. Eternity Flashlight

  5. Invented by… Pat Y Mah Daka Designs Ltd. Hong Kong

  6. Advantages No Batteries, no bulbs, Environmentally-friendly Super Bright LED (Light Emitting Diode) Only 30 seconds of shaking gives 5 minutes of light Does not burn-out like a typical light bulb Waterproof Great for emergency preparedness Shock resistant save money for batteries and replacement of bulbs Disadvantages More expensive Inconvenience of shaking before use

  7. BACK HOME*

  8. Michael Faraday • an English chemist and physicist • the discoverer of electro-magnetic induction, electro-magnetic rotations, the magneto-optical effect, diamagnetism, field theory and much more

  9. 1821 - plotted the magnetic field around a conductor carrying an electric current • 1831 - demonstrated the principle of induction an electric current could cause a magnetic field, a magnetic field should be able to produce an electric current

  10. Electromagnetic induction by using induction ring: the "induction" or generation of electricity in a wire by means of the electromagnetic effect of a current in another wire. The induction ring was the first electric transformer. • Magneto-electric induction: the production of a steady electric current. Faraday attached two wires through a sliding contact to a copper disc. By rotating the disc between the poles of a horseshoe magnet he obtained a continuous direct current. This was the first generator. Induction ring

  11. Faraday's law of induction • gives the relation between the rate of change of the magnetic flux through the surface S enclosed by a contour C and the electric field along the contour:

  12. Faraday’s Law of Electromagnetic induction: • The induced electromagnetic force in a circuit is directly proportional to the rate of change of magnetic flux through that circuit. • where ξ is the induced electromotive force and dΦ/dt is the time-rate of change of magnetic flux Φ. • The direction of the electromotive force (the negative sign in the above formula) was first given by Lenz's law, which means that the e.m.f. is induced to oppose the change.

  13. no. of turns in the coil induced e.m.f. In general, for a coil of N turns, the induced e.m.f. is given by

  14. The ammeter indicates currents in different directions depending on the relative motion of magnet and loop. • When the bar magnet is moved closer to, or farther from, the loop, an electromotive force (e.m.f.) is induced in the loop.  •  When the magnet stops moving, the current returns to zero as indicated by the ammeter.

  15. VIDEO

  16. Changing Magnetic Fields Cause Changing Flux       

  17. Eternity Flashlight

  18. Structure of Flashlight

  19. Working Principle of the Eternity Flashlight

  20. When the flashlight is shaken, a high strength magnet slides back and forth through a copper wire coil. EMF is then induced across the wire coil The electricity produced as a result is then stored in a capacitor instead of a battery. The torch uses the Faraday Law of Electromagnetic Induction to create the electricity it needs to charge itself. The Faraday Principle describes how a magnetic field can produce electric current in a wire that passes through it. coil magnet bumper bumper

  21. Capacitor • a basic electronic component that stores electric charge • used in the forever flashlight instead of a battery due to the fact that power is always available by shaking, thereby requiring less electricity storage than normal flashlights

  22. Rectifier • When the magnet is approaching and moving away from the coil, the induced e.m.f. in the coil flows in alternating directions. • However, if we need to store the charges in the capacitor, current should be flowing in one direction only. • Therefore, RECTIFIER is needed in order to store electric charge in the capacitors.

  23. Light Emitting Diode (LED) • The eternity flashlight uses an LED instead of a light bulb, and the white LED drains power from the capacitor. • an electronic component that emits light when an electric current is applied to it • long used for electronic indicator lights • High efficiency • Long lifespan • As the induced current of the coil inside the flashlight is small, LED is a perfect match for the design of this eternity flashlight. an LED Electronic LED Message Display

  24. Applications of electromagnetic induction

  25. 1. Moving coil Microphones

  26. Inside…… Inside……

  27. 2. Magnetic Tapes

  28. Magnetic powder Plastic coat Inside……

  29. 3. SQUIDS-Superconducting Quantum Interference Device

  30. CAMPING*

  31. Reference • http://www.dfaaward.com/trad/dfa2004_award.php# • http://emb.gov.hk/FileManager/TC/Content_4292/0479_daka.ppt • http://courses.science.fau.edu/~rjordan/rev_notes/28.2.htm • http://www.adventuregear.ca/gear/details/ee_forever.html • http://link.brightcove.com/services/link/Faraday+Flashlight_Faraday+Flashlight/bcpid1876250/bclid2457929/bctid2205605

  32. THE END~THANK YOU* Presented by : Elaine Chan Katherine Lam Helen Tai Vivian Tang

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