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Electromagnetic Induction

Electromagnetic Induction. What is electromagnetic induction? It is the production of an emf by a changing magnetic field. Faradays Law of electromagnetic induction The induced emf in a conductor is directly proportional to the rate of change of magnetic flux through the conductor.

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Electromagnetic Induction

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  1. Electromagnetic Induction

  2. What is electromagnetic induction? It is the production of an emf by a changing magnetic field. Faradays Law of electromagnetic induction The induced emf in a conductor is directly proportional to the rate of change of magnetic flux through the conductor. This is the principle behind the electric generator or dynamo. What is magnetic flux? Magnetic flux φ = B X A The unit of magnetic flux is the weber.

  3. To demonstrate electromagnetic induction (or Faradays Law)

  4. Mutual Induction Mutual induction occur when the changing magnetic field surrounding one coil causes an emf to be induced in a nearby coil.

  5. The transformer is a practical application of this principle

  6. Stepdown transformer

  7. The Transformer Equation NP = Number of turns in the primary Ns = Number of turns in the secondary Vin = Voltage in Vout = Voltage out

  8. Energy Losses in the transformer Ideally Power in = Power out (VI)IN=(VI)OUT

  9. Energy Losses in the transformer To reduce energy losses. • Laminate the core-this reduces currents induced in the core • The low voltage coil carries the greatest current so it should be made of thick wire which has low resistance. • The core is made of iron which is easy to magnetise and demagnetise.

  10. Self Induction The production of an emf in a coil due to its own changing magnetic field. To demonstrate self induction The neon lamp flashes when the switch is opened as the rapidly collapsing magnetic field induces a large emf in the coil. (self induction)

  11. Alternating Current This trace may be shown using an oscilloscope.

  12. RMS Values of AC When calculating power with AC always use the rms values not the peak values.

  13. AC and Capacitors A charged capacitor blocks DC but conducts AC.

  14. AC and inductors Inductors and AC Inductors act as resistors to AC. If the power source is DC the current through a coil is greater than if the power source is AC. This is due to the induced emf that opposes the applied emf. Uses of inductors Dimming stage lighting Tuning radios

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