2. http://www.geo.mtu.edu/weather/aurora/images/aurora/jan.curtis/index4.html http://science.nasa.gov/headlines/y2002/23sep_auroraseason.htm

4. Magnetic Fields – Long Straight Wire A current-carrying wire produces a magnetic field A current-carrying wire produces a magnetic field The compass needle deflects in directions tangent to the circle The compass needle deflects in directions tangent to the circle The compass needle points in the direction of the magnetic field produced by the currentThe compass needle points in the direction of the magnetic field produced by the current

5. Direction of the Field of a Long Straight Wire Right Hand Rule #2 Right Hand Rule #2 Grasp the wire in your right handGrasp the wire in your right hand Point your thumb in the direction of the currentPoint your thumb in the direction of the current Your fingers will curl in the direction of the fieldYour fingers will curl in the direction of the field

6. Magnitude of the Field of a Long Straight Wire The magnitude of the field at a distance r from a wire carrying a current of I is The magnitude of the field at a distance r from a wire carrying a current of I is µ o = 4  x 10 -7 T m / A µ o = 4  x 10 -7 T m / A µ o is called the permeability of free spaceµ o is called the permeability of free space

7. How big a field is produced by a current carrying wire? A very long wire! X B r B B =  o I/(2r)  o = 4 x 10 -7 Tm/A: permeability of FS

8. X Right-handed cork-screw rule XxxxxxXxxxxxXxxxxxXxxxxxXxxxxxXxxxxxXxxxxxXxxxxxXxxxxxXxxxxxXxxxxxXxxxxx...... x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x

9. I xo xo xo xo xo xo xo xo xo

10. http://www.bugman123.com/Physics/Physics.html For infinitely long solenoid B =  o nI n: number of turns/m

11. A solenoid electro-magnet is energized as shown in the figures. Since current flows through wire in the presence of magnetic fields, the solenoid will feel force. Which figure correctly describes the force acting on the solenoid?

13. I I xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.............................. xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx L r I1I1 I2I2 B =  o I 1 /2r F 2 = ILB =  o LI 1 I 2 /2r