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1: Chapter 30 Sources of the magnetic field
3: Cross product review
4: Right Hand Rule
5: Biot-Savart Law
6: Magnetic field of a long wire
7: Magnetic field due to a straight wire
8: B for a Curved Wire Segment Find the field at point O due to the wire segment
I and R are constants
q will be in radians
9: Magnetic field due to a current loop
10: Magnetic field due to a current loop
11: Comparison to an electric dipole
13: Force between two parallel wires
14: Force between two parallel wires
15: Historical definition of the Ampere
17: Introduction to Amperes Law
18: Amperes Law The integral is around any closed path
The current is that passing through the surface bounded by the path
Like Gausss Law, useful in finding fields for highly symmetric problems
19: Applying Amperes Law Select a surface
Try to imagine a surface where the electric field is constant everywhere. This is accomplished if the surface is equidistant from the charge.
Try to find a surface such that the electric field and the normal to the surface are either perpendicular or parallel.
Determine the charge inside the surface
If necessary, break the integral up into pieces and sum the results.
Select a path
Try to imagine a path where the magnetic field is constant everywhere. This is accomplished if the surface is equidistant from the charge.
Try to find a path such that the magnetic field and the path are either perpendicular or parallel.
Determine the current inside the surface
If necessary, break the integral up into pieces and sum the results.
20: Example: Magnetic field inside a wire
21: Example: Solenoid
22: Example: Solenoid
23: Example: Toroid
25: Magnetic Flux The magnetic field in this element is B
dA is a vector that is perpendicular to the surface
dA has a magnitude equal to the area dA
The magnetic flux FB is
The unit of magnetic flux is T.m2 = Wb
Wb is a weber
26: Gauss Law in Magnetism Magnetic fields do not begin or end at any point
The number of lines entering a surface equals the number of lines leaving the surface
Gauss law in magnetism says:
27: Displacement Current Amperes law in the original form is valid only if any electric fields present are constant in time
Maxwell added an additional term which includes a factor called the displacement current, Id
The displacement current is not the current in the conductor
Conduction current will be used to refer to current carried by a wire or other conductor
28: Amperes Law General Form Also known as the Ampere-Maxwell law
Magnetic fields are produced both by conduction currents and by time-varying electric fields
29: Ferromagnetism Domains
Curie Temperature
Electron orbits align with an external magnetic field