1. Electromagnetism Continued

2. Magnetic field lines produced by a magnetic dipole form a pattern similar to the electric field lines produced by an electric dipole. However, the magnetic field lines form continuous loops.

3. A magnetic dipole lines up with an externally produced magnetic field just as an electric dipole lines up with an electric field.

4. The magnetic field of the earth can be pictured by imagining a bar magnet inside the earth, oriented as shown here.

5. The right-hand rule gives the direction of the magnetic field lines that encircle a current-carrying wire. The thumb points in the direction of the current and the fingers curl in the direction of the field lines.

6. When a current-carrying wire is bent into a circular loop, the magnetic fields produced by different segments of the wire add to produce a strong field near the center of the loop.

7. Electromagnet (Magnetism from Electricity)
An electromagnet is simply a coil of wires which, when a current is passed through, generate a magnetic field, as below.

8. With the wire oriented along a north-south line, the compass needle deflects away from this line when there is current flowing in the wire.

9. A Ferromagnet in the Middle
If we look at a solenoid, but rather than air, wrap it around a nice iron core. What happens to the change in flux for a given current?
Can you see why ferromagnetic materials are often put in the middle of current-carrying coils?

10. Making a Magnet from a Ferromagnetic Material
• domains in which the magnetic fields of individual atoms align
• orientation of the magnetic fields of the domains is random
• no net magnetic field.
• when an external magnetic field is applied, the magnetic fields of the individual domains line up in the direction of the external field
• this causes the external magnetic field to be enhanced

11. Think Pair Share Name 2 types of magnets that we’ve discussed
How can we control the motions of two different magnets?
How can we generate a force on a current conducting wire?

12. Observations:
Two parallel current-carrying wires exert an attractive force on each other when the two currents are in the same direction.
Video
A current conducting wire is placed in a shoehorn magnet and electricity is put through the wire

13. The magnetic force exerted on the moving charges of an electric current is perpendicular to both the velocity of the charges and to the magnetic field.

14. Magnetic Force on Current-Carrying Wire
Since moving charges experience a force in a magnetic field, a current-carrying wire will experience such a force, since a current consists of moving charges. This property is at the heart of a number of devices.

15. If the fingers of the right hand points in the direction of the magnetic field, and the thumb in the direction of the (conventional) current, the palm indicates the direction of the magnetic force.

16. Electric Motor
An electric motor, is a machine which converts electrical energy into mechanical (rotational or kinetic) energy.   
A current is passed through a loop which is immersed in a magnetic field. A force exists on the top leg of the loop which pulls the loop out of the paper, while a force on the bottom leg of the loop pushes the loop into the paper.
The net effect of these forces is to rotate the loop.

17. Summary of magnetic forces
Moving charges inside a conductor will generate a magnetic field around the conductor.
If the conductor (wire) is in a permanent magnetic field, the two fields (permanent & generated) will interact and there will be a force between them (R/L hand rules).