ch36_jdzr

Zach Rosinger Jon Difiore Pd. #8

Chapter 36 Magnetism:
36.1 Magnetic Poles: Magnets exert forces on each other which are similar to electric charges. Both can attract and repel without directly touching. **Magnetic poles** produce magnetic forces just as electric charges produce electrical forces. In a compass, the end that is north, is considered to be the north-seeking pole of the earth. The end that is labeled south is considered to be south-seeking. This makes the north pole have a magnetic charge of south, and the south pole to have a magnetic charge of north. This can be seen when a north end of a compass is brought up to a north pole of a magnet, and the two repel. This occurs because both are north seeking, and that makes the two of them repel since they are like charges. An important difference between magnetic poles and electric ones is that electric poles can be isolated whereas magnetic ones cannot.

Magnetic field--**the space around a magnet in which a magnetic force is exerted. The shape of the field can be observed easily when a cluster of iron filings are dropped around a magnet, you can see the paths they take around the magnet and this shows the field lines.
 * 36.2 Magnetic Fields:

Magnetic fields are a relative by-product of the electric field. The magnet is composed of millions of small atoms that are all in motion which is what causes the magnetism to begin with. Electrons spin on their own axes which cause a charge in motion, creating another magnetic field. Every spinning electron is a mini-magnet, and when electrons spin in the same direction as others around them, it makes a stronger magnet. In most atoms the electrons movement cancel each other out, which is why everything is not magnetic. **
 * 36.3 The Nature of a Magnetic Field:



Magnetic domains** are clusters of aligned atoms. This occurs when a magnetic field is strong enough to align a large amount of atoms.
 * 36.4 Magnetic Domains:



The only difference between a piece of iron and a magnetized piece of iron is the alignment of the domains. The ability for iron alloys to be magnetized differs depending on the type, softer alloys are easier to align, whereas stronger ones are much more difficult. An example would be soft iron compared to steel. When a permanent magnet is either dropped, or heated, some of the domains are jostled out of place slightly, which is why it is not good to drop a magnet. The domains can become mixed up and then the magnet would no longer be magnetized, making it a simple piece of iron or whatever the material was.

A moving charge produces a magnetic field. An electric current can also produce a magnetic field. If a wire is bent into a loop, and electrical current is passed through it, then the magnetic field surrounding the loop is stronger since the whole material is closer together. A current carrying coil of wire with many loops is called an Electromagnet.**
 * 36.5 Electric Currents and Magnetic Fields:



A charged particle will not interact with a static, or un-moving magnetic field. A charged particle experiences a deflecting force when the charged particle is moving in a magnetic field. This force is greatest when the particle moves in a direction perpendicular to the magnetic field lines. At other positions the force is less, and becomes zero when it becomes parallel. This concept is used in a practical way by the television, which uses magnetic and electrical charges to cause the deflection and eventually a picture.
 * 36.6 Magnetic Forces on Moving Charged Particles:**

Moving charges on a wire will transfer the force to the wire causing movement to occur. If the direction of the current in the wire is reversed, the deflecting force acts in the opposite direction. The direction of the force is always a sideways force.
 * 36.7 Magnetic Forces on Current-Carrying Wires:**

//Ammeter// is used to measure currrent in amperes, a //Voltmeter// measures electric potential or volts. These are both from a galvanometer and the way to change between the two would just be a different calibration. You can design an electric motor by slightly altering the design of the galvanometer. The basic design of a dc motor would be a rotating looped wire through a magnetic field that goes to stationary contatcts and leads to creating current.
 * 36.8 Meters to Motors:**

The reason why a magnet faces north is because it is north-seeking, not north charged. The north pole of the Earth is actually south charged, and therefore looks for the north charge, making it north-facing. The same is for the south pole only the opposite. The discrepency that exists between the orientation of a compass and the actual north part of the earth is called magnetic declination. There is a theory, that has not yet been proven, that the reason for the earth being magnetic to begin with is that the convection currents in the molten parts of the earth's interior cause a magnetic field. More than 20 reversals have taken place in the past 5 million years. The most recent one most likely occured 700,000 years ago.
 * 36.9 The Earth's Magnetic Field:**