Advanced Physical Science

Magnetism  Magnetism: The ability of some substances to attract iron, steel, and some other metals  Magnetism is a property of moving e-  Every moving e- has a magnetic field around it  Each e- in every atom is a tiny magnet

Magnetic Domain Electrons are negatively charge particles that move around the nucleus of atoms Moving electrons produce magnetic fields that give atoms a N and S pole In most materials (like Copper and Aluminum) magnetic fields cancel each other out. Result: the object is not magnetic

Magnetic Domain (cont)  In some materials (like iron, nickel and cobalt), the atoms group together in tiny regions called domains.  Domains are like tiny magnets of different sizes within an object.

Magnetic Poles  Like poles repel  Unlike poles attract  Broken magnets create new poles

Magnetic Field  Area around a magnet where magnetic forces act  Forces are in a specific direction shown by field lines  The lines map the strength of the magnetic field (stronger at poles) Iron filings placed around a magnet will show the shape of the magnetic field around the magnet

Permanent Magnets  Made from magnetic material (an alloy of aluminum, nickel, and colbalt) and have a persistent magnetic field  Retain magnetic properties better than other materials  A strong current is used to align the domains of the alloy  Once the domains are lined up, they tend to remain that way

Making a Magnet  A magnet can be made by aligning domains in an object  Example: An iron nail can be magnetized if you rub it in one direction with one pole on a magnet  The magnetic field of the magnet will cause the domains in the nail to rotate and align with the magnet

Losing Magnetism  Magnets can lose magnetism if domains of a magnets become unaligned  Things that cause magnet to get out of alignment: Dropping a magnet Heating a magnet

Magnetism from Electricity  An electric current will produce a magnetic field  Electromagnetism: The interaction between electricity and magnetism

Magnetism from Electricity: Solenoids  A coil of wire that produces a magnetic field when carrying an electric current  Increase strength of magnetic field produced by solenoid by… Adding more loops Increasing the current in the wire

Magnetism from Electricity: Electromagnets  Temporary magnet formed by placing iron inside a current carrying wire (electricity)  Magnetic field is only present when current is flowing  Strength of magnetic field is increased by adding more turns of the wire or by increasing the amount of current through the wire.  Magnetic properties can be controlled by changing the current.

Examples of Electromagnets Maglev Train, Japan Electromagnet in a salvage yard, turned on and off to lift scrap metal Press the doorbell, switch in solenoid circuit closes, electric current created, iron rod is pulled through solenoid, rod strikes bell

Electricity from Magnetism: Electromagnetic Induction  Magnetic Field can produce an electric field  The size of electric current depends… Number of wire loops How fast move magnet  The direction depends on Whether magnet is pulled or pushed

Electricity from Magnetism (cont)  In previous example, electric current induced by moving the magnet  Electric current can also be induced by moving the wire

Application of Electromagnetic Induction: Generator  Converts MECHANICAL ENERGY to ELECTRICAL ENERGY  A generator rotates a coil of wire through a magnetic field  The changing magnetic field around the wire induces electric current in the wire  The electric current produced by a generator changes direction each time the coil makes a ½ turn ALTERNATING CURRENT (AC)

Transformer  Increases or decreases the voltage of an alternating current  Consists of 2 coils wrapped around an iron ring  Step-up transformer: Increases voltage  Step-down transformer: Decreases voltage

Electrical Energy to your Home  Generator at the power plant produces electric current with HIGH voltage  Step-up transformers increase the voltage in order to decrease loss of POWER that occurs during transmission over long distance  Step-down transformers decrease the voltage before the electric current reaches consumers

How Electricity Gets to Your House  Electricity is made at a power plant by huge generators (HIGH voltage) Most power plants use coal, but some use natural gas, water or even wind.  The current is sent through transformers to INCREASE THE VOLTAGE to push the power long distances.  The electrical charge goes through high- voltage transmission lines that stretch across the country.  It reaches a substation, where the VOLTAGE IS LOWERED so it can be sent on smaller power lines

How Electricity Gets to your House (cont.)  It travels through distribution lines to your neighborhood, where smaller pole-top transformers reduce the voltage again to take the power safe to use in our homes.  It connects to your house through the service drop and passes through a meter that measures how much our family uses.  The electricity goes to the service panel in your basement or garage, where breakers or fuses protect the wires inside your house from being overloaded.  The electricity travels through wires inside the walls to the outlets and switches all over your house.

FYI…Nuclear Power Plant  Thermal Energy from a nuclear reaction boils water to produce steam  The steam turns a turbine  The turbine turns the magnet of the generator, inducing electric current and generation electrical energy.