Magnetic force Apr. 23, 2007

+ Magnetic force (Sect 5.12)
In a thin wire
Note: for force between two current elements, find due to element 1 onto element 2 by assuming that the element 2 does not generate .

+ Application: charge separator, velocity filter (find such that ); motor.

+ Magnetic dipole (Sect. 5.5): a small current loop; measure by magnetic moment product of current and loop area with direction perpendicular to the loop and follows the right hand rule.

+ Magnetic materials (Sect. 5.6): their magnetic property is measured by magnetization magnetic moment per unit volume.

+ gives the enhancement on when an external is applied. It can be thought of being generated by internal bound current:
or ; or
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HW #21 (no late homework) Due 4/26/07
1. a) A infinitely long filamentary wire carries a current of 5A in the +z direction. Calculate i) at (-8, 6, 7), ii) the flux through the square loop described by , , ; b) if A/m on plane z=0, determine the current density.

2. Exercise 5.5 (page 186) (do not forget the specify the direction of the field)
3. Exercise 5.4 (page 185) (Apply equation from example 4.9 on the web and look at example 5.4 page 184 in the text).
Extra-credit
Consider the disk on Fig. 3-11 (page 96) has uniform surface current density . Find the magnetic flux density along z axis.