Magnetic Forces and Magnetic Field Lecture

Magnetic Forces and Magnetic Field

1. Magnetic Forces and Magnetic Field

2. Review Types of Magnetic Materials Diamagnetic Materials – weakly respond to a magnetic field. -magnetization exists only when an external magnetic field is applied. -the magnetic domains align themselves opposite the applied magnetic field -instead of being attracted, diamagnetic materials are repelled by a magnetic field. -metals, nonmetals, water, and organic compounds are diamagnetic.

3. Review Types of Magnetic Materials Paramagnetic Materials – have net magnetic moments due to unpaired electrons. -they are weakly attracted to magnets . -transition metals such as palladium, platinum, and actinide elements are paramagnetic. -paramagnetic become more magnetic when cooled .

4. Review Types of Magnetic Materials Ferromagnetic Materials – are strongly attracted by a magnet -ferromagnetic materials contain some unpaired electrons, thus, their atoms initially have magnetic properties even in the absence of an external magnetic field. -When heated to a sufficiently high temperature, ferromagnetic materials lose their magnetic properties. This temperature is called Curie Temperature (also called Curie Point ) -the Curie Temperature for cobalt, iron, and nickel are 1131 C, 770 C, and 358 C, respectively.

5. Summary Most materials are either weakly attracted (paramagnets) or weakly repelled (diamagnets) by magnets. Diamagnetism is an inherent property of all materials, and it arises from Lenz's laws. Paramagnetism is seen in materials whose atoms have at least one unpaired electron.

6. Magnetic Field A magnetic field is a region of space, which has the ability to exert a magnetic force on magnetic dipoles and on moving electric charges . Magnetic field exists around permanent magnets , current-carrying conductors , and other magnetic materials .

7. Sample Problems 1. A proton moves through a uniform magnetic field of magnitude 2.0 𝝁T at a speed of 5x10 6 m/s. (a) What is the magnitude of the maximum magnetic force it can experience? (b) If the proton is replaced by an electron, will it experience the same maximum force?

8. Motion of a Charged Particle in a Magnetic Field Magnetic force , being a cross product of velocity and magnetic field, is always perpendicular to the plane formed by the velocity vector and magnetic field vector.