Magnetism Applied Physics Chap 7

Magnetite: Or “lodestone” is a naturally magnetic ore of Iron Oxide originally found in the region called “Magnesia” which is now part of Turkey. Applied Physics Chap 7

In general, permanent Magnets are made from Iron, nickel, or cobalt metals due to the arrangement of the electrons in these atoms. Nickel #28 Iron #26 Cobalt #27 Recently, extremely strong magnets have been made out of the rare earth metal “neodymium” Applied Physics Chap 7

Magnetism: The property of matter in which there is a force of attraction or repulsion between unlike of like poles. Permanent Magnets: magnets that maintain their magnetic properties for long periods of time Applied Physics Chap 7

Magnets have two poles (called North and South) Magnetic Poles: regions on a magnet where the magnetic force originates. Magnets have two poles (called North and South) Magnetic Field: the space around a magnet where magnetic force pushes or pulls against other magnets. Applied Physics Chap 7

Magnetic domains: a microscopic cluster of atoms that are all lined up in the same direction. Metals like iron have microscopic, interlocking crystals that form as the molten metal cools. A strong magnet is one where most of the crystals are aligned in the same direction reinforcing the magnetic field. Applied Physics Chap 7

Taking care of Permanent Magnets Un-magnetized iron, can be “magnetized” by stroking in a single direction with a strong magnet. This forces all the magnetic domains to line up in the same direction. Magnets can be “de-magnetized” by a.) stroking with a strong magnet in the opposite direction. b.) heating the magnet up c.) hitting the magnet with a hammer Applied Physics Chap 7

The Earth’s Magnetic Field Compasses are small magnets, free to turn, that align themselves with the Earth’s magnetic field. The Earth’s core is solid Iron and Nickel metal surrounded by an outer core of liquid iron/nickel metal. The core is rotating, at a slightly different speed than the overall planet’s. This rotation of the core forms an electromagnet. Applied Physics Chap 7

Lines of magnetic force Applied Physics Chap 7

Electromagnetic induction: the production of a current in a circuit by changing the strength, position, or orientation of an external magnetic field. Faraday’s Law: An electric current can be produced in a circuit by a changing magnetic field, or by moving a conductor through a magnetic field. Applied Physics Chap 7

Magnetic Forces on Moving charged Particles. A charged particle moving through a magnetic field will feel that magnetic force perpendicular to the direction of its motion. Applied Physics Chap 7

A conductor, carrying a current will feel a force, depending on the direction of a current. Applied Physics Chap 7

A galvanometer is a device composed of a rotating part called a “rotor” , that is surrounded by a coil of wire. More current in the wire causes the rotor to move (usually resisted by a spring) Stronger currents move the rotor further indicating the strength of the current. Applied Physics Chap 7

Generator: a device that uses electromagnetic induction to convert mechanical energy to electrical energy. A generator is a mechanical device that causes a coil of wire to rotate through the magnetic field from a set of permanent magnets, forcing a current to flow through the coil. Applied Physics Chap 7

In a motor, electrical energy is converted into mechanical energy. Motor: a mechanical device built similarly to a generator that uses the force generated by moving a current through a conductor to turn a rotor. In a motor, electrical energy is converted into mechanical energy. Applied Physics Chap 7

Electrical Energy: the energy associated with electrical charges, whether moving or at rest which is measured in Joules.   Watt: the SI unit of power equal to the work done by 1 Joule of energy in 1 second. Applied Physics Chap 7

Step 1, calculate the power used in watts and convert to kilowatts Electric power companies use the Kilowatt-hour as a measure of electrical energy consumed by a household or business. Step 1, calculate the power used in watts and convert to kilowatts Step 2 multiply by the hours of usage Step 3 add the power used from all sources during a time period. Step 4 Multiply by the utility cost per kilowatt- hour of power usage. Applied Physics Chap 7