Question

Physics Prelab: Magnetism

Watch the video on magnetism. Explain how the “two” right hand rules works –what does each indicate?

How do magnetic fields get their start - what causes magnetic fields?

What is the force a magnetic field exerts on a charged particle?  Write down the equation and explain the direction.

Explain how a solenoid works - how does it produce a magnetic field?

What are the five major types of magnetic materials? Describe each briefly.

Answer 1

The right hand rule states that, to find the direction of the magnetic force on a positive moving charge, the thumb of the right hand point in the direction of v, the fingers in the direction of B, and the force (F) is directed perpendicular to the right hand palm.

A magnetic field is produced whenever an electrical charge is in motion. The spinning and orbiting of the nucleus of an atom produces a magnetic field as does electrical current flowing through a wire. The direction of the spin and orbit determine the direction of the magnetic field.

Magnets causes magnetic field.

The magnitude of the magnetic force FF on a charge qq moving at a speed vv in a magnetic field of strength BB is given by:

F=qvBsin(θ)F=qvBsin(θ)

where θ is the angle between the directions of v and B.

A solenoid is a coil of wire in a corkscrew shape wrapped around a piston, often made of iron. As in all electromagnets, a magnetic field is created when an electric current passes through the wire. Electromagnets have an advantage over permanent magnets in that they can be switched on and off by the application or removal of the electric current, which is what makes them useful as switches and valves and allows them to be entirely automated.

Like all magnets, the magnetic field of an activated solenoid has positive and negative poles that will attract or repel material sensitive to magnets. In a solenoid, the electromagnetic field causes the piston to either move backward or forward, which is how motion is created by a solenoid coil.

There are Five types of magnetic materials. Examples of magnetic materials are:

• Paramagnetic materials
• Diamagnetic materials
• Ferromagnetic materials
• Ferrimagnetism
• Antiferromagnetism

Paramagnetic materials: Paramagnetic Materials: These are metals that are weakly attracted to magnets. They include aluminum, gold, and copper. The atoms of these substances contain electrons most of which spin in the same direction ... but not all . This gives the atoms some polarity.

Diamagnetic materials: Diamagnetic materials are those that some people generally think of as non-magnetic, and include water, wood, most organic compounds such as petroleum and some plastics, and many metals including copper, particularly the heavy ones with many core electrons, such as mercury, gold and bismuth.

Ferromagnetic materials: Ferromagnetic materials are those materials which exhibit a spontaneous net magnetization at the atomic level, even in the absence of an external magnetic field. When placed in an external magnetic field, ferromagnetic materials are strongly magnetized in the direction of the field.

Ferrimagnetism: a ferrimagnetic material is one that has populations of atoms with opposing magnetic moments, as in antiferromagnetism; however, in ferrimagnetic materials, the opposing moments are unequal and a spontaneous magnetization remains.

Antiferromagnetism: Antiferromagnetic materials occur commonly among transition metal compounds, especially oxides. Examples include hematite, metals such as chromium, alloys such as iron manganese (FeMn), and oxides such as nickel oxide (NiO). There are also numerous examples among high nuclearity metal clusters.