1. Recall: Magnetic Domains
Domains are micro-regions of a magnetic material with net magnetic pole orientations.
When the domains are all unaligned in a magnetic material, the object produces no external magnetic field.

2. Magnetic Domains
When most of the domains are all lined up in a magnetic material, the object produces an external magnetic field.
Actually, when an external magnetic field is present, it can help domains to line up, creating a temporary magnet.

3. Action at a Distance An example of domains lining up due to an external magnetic field.
Magnetic field lines are the result of a magnet inducing a temporary alignment of the domains within a group of iron filings.
Iron filings are relatively easy objects to induce a domain alignment within.
Magnetic Induction: Inducing field alignment using an external magnetic field.

4. F
Field Lines and Force
Magnetic Fields: The unseen property that is emitted by a magnetic material. The strength of a magnetic field is shown visually using field lines.
Field density (or field strength): is indicated by lines and how close together they are represented.

5. Oersted’s Discovery: Right-hand Rule #1 For straight conductors:
The right hand rule is a strategy for remembering the magnetic field form generated by flowing current (I).

6. Fields from Current (a second look from yesterday’s lesson)
When the current flows from left to right,
The field generated looks like this
Based on right hand rule #1 for straight conductors.

7. Field drawings from the end of a conductor
When viewing a cross section of a current carrying wire, a dot represents current flowing out of the page,
And an X represents current flowing into the page.
The right and rule for straight conductors still applies.
Check the diagrams with your right hand!

8. think and do

9. think and do

10. Indicate the current direction for each of the diagrams.
think and do
Indicate the current direction for each of the diagrams.

11. NEW!!!!!A Magnetic field for a current Carrying Coil (aka…A Solenoid)
By following a loop with the right hand rule for straight conductors we can develop a rule for the magnetic field produced by coils carrying current (called solenoids).

12. Solenoid Field Shape
The current seems to cause the magnetic field to “spew” out from the centre of the coil so that if we could see these field lines in 3 dimensions it might look like a donut.

13. Solenoids (tightly wound helix, carrying current)
The field generated by a solenoid has a north pole and a south pole. It is made up of multiple loops.
There is a 2nd right hand rule that describes the field of a solenoid.

14. Right Hand Rule#2: For Solenoids
The right hand rule for solenoids requires you to curl wrap your fingers around the helix in the direction of current flow.
Usually a core is placed within a solenoid.
The domains of the core help to reinforce the strength of the electromagnet.

15. Visualizing the Solenoid Right Hand Rule

16. Solenoids strength is determined by two factors,
Write
Solenoids strength is determined by two factors,
1) The amount of current flowing
2) The number of loops in the coil

17. Practice Problem #1
Current flow
Current flow

18. Ferrofluids
Ferrofluids are extensively used for the study of magnetic domain structures in magnetic tapes, rigid and floppy disks, magneto-optical disks, crystalline and amorphous alloys, garnets, steels and geological rocks.