Содержание
- 2. Lecture 11 Currents in Metals The effects of magnetic fields. The production and properties of magnetic
- 3. Types of Conductivity Conductors are materials through which charge moves easily. Insulators are materials through which
- 4. Drift speed of electrons There is a zigzag motion of an electron in a conductor. The
- 5. So when we consider electric current as a flow of electrons: in reality there happens zigzag
- 6. Current in metals Every atom in the metallic crystal gives up one or more of its
- 7. Resistivity A conductor with current: Current density: I – electric current A – the cross-sectional area
- 8. Conductivity A current density J and an electric field E are established in a conductor whenever
- 9. Ohm’s law again For many materials (including most metals), the ratio of the current density to
- 10. Magnets A single magnetic pole has never been isolated. Magnetic poles are always found in pairs.
- 11. Magnet Poles Magnet field lines connect unlike poles. Magnet field lines repels from like poles.
- 12. Magnet Force The magnitude FB of the magnetic force exerted on the particle is proportional to
- 13. The text in the previous slide can be summarized as: So the units for B are:
- 14. Direction of FB Right hand rule: The fingers point in the direction of v, with B
- 15. Magnetic field direction Magnetic field lines coming out of the paper are indicated by dots, representing
- 16. Magnetic Force on a Current Magnetic force is exerted on a single charge moving in a
- 17. n is the number density of charged particles q vd is the drift speed of q
- 18. Arbitrary shaped wire The force on a small segment of an arbitrary shaped wire is: The
- 19. as B is uniform: The magnetic force on a curved current-carrying wire in a uniform magnetic
- 20. So, the force on a straight wire in a uniform magnetic field is: is a vector
- 21. Loop Wire in a Uniform Magnetic field The net magnetic force acting on any closed current
- 22. Current Loop Torque in a Uniform Magnetic Field - Overhead view of a rectangular loop in
- 23. When the magnetic field is parallel to the plane of the loop, the maximal torque on
- 24. When the loop is not parallel to the magnetic field, i.e. the angle between A and
- 25. In formula for torque we have vector A: - Its direction is perpendicular to the plane
- 26. Right – hand rule for loop The direction of the magnetic moment is the same as
- 27. Magnetic Moment The vector product IA is defined to be the magnetic dipole moment μ (often
- 28. Potential Energy of a Magnetic Moment The potential energy of a system having magnetic dipole μ
- 29. Motion of a Charged Particle in a Uniform Magnetic Field When the velocity of a charged
- 30. Using the obtained formula we get the angular velocity here v is perpendicular to B.
- 31. Lorentz Force In the presence of E and B, the force acting on a charged particle
- 32. The Hall Effect When a current-carrying conductor is placed in a magnetic field, a potential difference
- 33. the magnetic force exerted on the carriers has magnitude qvdB. this force is balanced by the
- 34. Using that A=td – cross sectional area of the conductor, t – thickness of the conductor
- 35. When the charge carriers in a Hall-effect apparatus are negative, the upper edge of the conductor
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