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Transformers

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PowerPoint slides to teach transformers

PowerPoint slides to teach transformers

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  • 1. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> ScienceCafe TRANSFORMERS K Warne
  • 2. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> ScienceCafe Magnetic Effect A magnetic field is generated around any conductor when an electric current flows through it. Electric current Wire with current coming towards you Wire with current going away from you x
  • 3. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> ScienceCafe Mutual Induction • MUTUAL INDUCTION is defined as the changing electric …………………… producing a changing …………………….. field which can produce a changing ………………….. in another conductor. • This is the basic principle of the ……………………… ~
  • 4. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> ScienceCafe Transformers• Coils of insulated conducting wire are wound around a ring of iron constructed of thin isolated laminations or sheets. • The laminations minimize eddy currents in the iron. • Eddy currents are circulatory currents induced in the metal by the changing magnetic field. These currents produce an undesirable by-product—heat in the iron. • Energy loss in a transformer can be reduced by using thinner laminations, very “soft” (low-carbon) iron and wire with a larger cross section, or by winding the primary and secondary circuits with conductors that have very low resistance. • Transformers used to transmit and distribute power are commonly 98 to 99 percent efficient. • While eddy currents are a problem in transformers, they are useful for heating objects in a vacuum.
  • 5. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> ScienceCafe SOLENOID A coil generates a very concentrated (strong) magnetic field in its center. Electric current x N S x x Increasing the number of coils strengthens the magnetic field. The Right Hand Rule can also be applied to a solenoid! INSIDE THE COIL THE FIELD GOES FROM SOUTH TO NORTH!!!
  • 6. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> ScienceCafe Transformers• Ideally – all magnetic flux from primary coil links with secondary coil. • The number of turns of wire is directly proportional to the voltage in the coil. Np Vp Ns Vs — = — How many turns of wire would you need in a transformer that has 1000 turns in the primary and needs to step down the voltage from 220V to 9V? ........... Voltage A. C in. ............. Voltage A. C OUT. STEP ................TRANSFORMER .......... turns .......... turns Vp = Vs Np Ns
  • 7. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> ScienceCafe Transformers From Faraday’s Law: “The size of the induced current is directly proportional to the rate of change of the magnetic flux linkage.” • Therefore: work done by primary = energy gained by secondary Since W = QV and Q = It .: W = VIt Wp = Ws ......... = ........... ........... = ............. ......... = ........... Calculate the current in the secondary coil of the 220V/9V transformer if the current in the primary was 1.5A
  • 8. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> ScienceCafe Hi - This is a SAMPLE presentation only. My FULL presentations, which contain loads more slides and other resources, are freely available on my resource sharing website: www.sciencecafe.org.za (paste into your browser if link above does not work) Have a look and enjoy! Keith Warne