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Chapter 34. Electromagnetic Induction

Chapter 34. Electromagnetic Induction. Electromagnetic induction is the scientific principle that underlies many modern technologies, from the generation of electricity to communications and data storage. Chapter Goal: To understand and apply electromagnetic induction.

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Chapter 34. Electromagnetic Induction

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  1. Chapter 34. Electromagnetic Induction Electromagnetic induction is the scientific principle that underlies many modern technologies, from the generation of electricity to communications and data storage. Chapter Goal: To understand and apply electromagnetic induction.

  2. Chapter 34. Electromagnetic Induction Topics: • Induced Currents • Motional emf • Magnetic Flux • Lenz’s Law • Faraday’s Law • Induced Fields • Induced Currents: Three Applications • Inductors • LC Circuits • LR Circuits

  3. Chapter 34. Reading Quizzes

  4. Currents circulate in a piece of metal that is pulled through a magnetic field. What are these currents called? • Induced currents • Displacement currents • Faraday’s currents • Eddy currents • This topic is not covered in Chapter 34.

  5. Currents circulate in a piece of metal that is pulled through a magnetic field. What are these currents called? • Induced currents • Displacement currents • Faraday’s currents • Eddy currents • This topic is not covered in Chapter 34.

  6. Electromagnetic induction was discovered by • Faraday. • Henry. • Maxwell. • Both Faraday and Henry. • All three.

  7. Electromagnetic induction was discovered by • Faraday. • Henry. • Maxwell. • Both Faraday and Henry. • All three.

  8. The direction that an induced current flows in a circuit is given by • Faraday’s law. • Lenz’s law. • Henry’s law. • Hertz’s law. • Maxwell’s law.

  9. The direction that an induced current flows in a circuit is given by • Faraday’s law. • Lenz’s law. • Henry’s law. • Hertz’s law. • Maxwell’s law.

  10. Chapter 34. Basic Content and Examples

  11. Faraday’s Discovery Faraday found that there is a current in a coil of wire if and only if the magnetic field passing through the coil is changing. This is an informal statement of Faraday’s law.

  12. Magnetic data storage encodes information in a pattern of alternating magnetic fields. When these fields move past a small pick-up coil, the changing magnetic field creates an induced current in the coil. This current is amplified into a sequence of voltage pulses that represent the 0s and 1s of digital data.

  13. Motional emf The motional emf of a conductor of length l moving with velocity v perpendicular to a magnetic field B is

  14. EXAMPLE 34.1 Measuring the earth’s magnetic field QUESTION:

  15. EXAMPLE 34.1 Measuring the earth’s magnetic field

  16. EXAMPLE 34.1 Measuring the earth’s magnetic field

  17. EXAMPLE 34.1 Measuring the earth’s magnetic field

  18. Magnetic flux can bedefined in terms of an area vector

  19. Magnetic Flux The magnetic flux measures the amount of magnetic field passing through a loop of area A if the loop is tilted at an angle θ from the field, B. As a dot-product, the equation becomes:

  20. EXAMPLE 34.4 A circular loop in a magnetic field QUESTION:

  21. EXAMPLE 34.4 A circular loop in a magnetic field

  22. Lenz’s Law There is an induced current in a closed, conducting loop if and only if the magnetic flux through the loop is changing. The direction of the induced current is such that the induced magnetic field opposes the change in the flux.

  23. Tactics: Using Lenz’s Law

  24. Faraday’s Law An emf is induced in a conducting loop if the magnetic flux through the loop changes. The magnitude of the emf is and the direction of the emf is such as to drive an induced current in the direction given by Lenz’s law.

  25. Problem-Solving Strategy: Electromagnetic Induction

  26. Inductance of a solenoid The inductance of a solenoid having N turns, length l and cross-section area A is

  27. EXAMPLE 34.12 The length of an inductor QUESTION:

  28. The potential difference across an inductor The potential difference across an inductor with an inductance of L and carrying a current I is

  29. EXAMPLE 34.13 Large voltage across an inductor QUESTION:

  30. EXAMPLE 34.13 Large voltage across an inductor

  31. EXAMPLE 34.13 Large voltage across an inductor

  32. EXAMPLE 34.13 Large voltage across an inductor

  33. The current in an LC circuit The current in an LC circuit where the initial charge on the capacitor is Q0 is The oscillation frequency is given by

  34. EXAMPLE 34.15 An AM radio oscillator QUESTION:

  35. EXAMPLE 34.15 An AM radio oscillator

  36. Chapter 34. Summary Slides

  37. General Principles

  38. General Principles

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