Chapter 8 Electricity, Magnetism and its uses General Properties of Magnets Magnetism: comes from the region in Greece called Magnesia that contained certain rocks called lodestones that produced forces between each other. They were stones that contained iron ore called magnetite. The Chinese used them early in the 12th century to navigate their ships

Magnetic Poles Like electric charges magnetic poles produce forces that are broken down into north and south seeking poles. The strength of their interaction depends on the distance between the poles. Like poles repel and opposites attract.

Magnetic Field The magnetic field is the space around the magnet in which the force is exerted and is represented by field lines (just like electric field lines).

Lines go from north to south so arrows will always point away from north and toward south

Magnetic domains A microscopic cluster of atoms with their magnetic fields aligned. Made up of billions of atoms that are aligned either to the north or south pole. Their strength is represented by arrows and the number and alignment of arrows shows the strength of the magnet.

Magnetic Materials Iron, cobalt, and nickel are magnetic elements because their atoms behave like magnets. Common definition of magnetism is the ability to attract iron. Steel is magnetic because it is an alloy that contains iron.

Random and aligned arrangements of domains.

Electromagnetism Electromagnetism is magnetism produced by electric charge in motion. Electromagnetic induction is the production of a magnetic force in a conducting circuit by changing the strength, position, or orientation of an external magnetic field. This can be done by using a coil of wire wrapped around a moving magnetic object. The more coils of wire, the stronger the magnetic field will be and more voltage will be produced.

Electromagnetism Faraday’s Law states that the induced voltage in a coil is proportional to the product of the number of loops and the rate at which the magnetic field changes within those loops. (how fast the magnet is moving inside the coils).

Electromagnetic Induction is the process of producing an electric current by moving a loop of wire through a magnetic field A galvanometer is an instrument that uses an electromagnet to measure electric current

Current AC current (alternating current) can reverse the direction of the flow while keeping in a regular pattern DC current (direct current) can not change directions; will flow only in one direction The strongest magnetic forces are located at the magnetic poles Current that flows in an electric circuit carries electrical energy A switch that reverses the direction of the current in a motor is a commutator

Generators, Motors, and Transformers The function of an electric motor is to convert electrical energy to mechanical energy The function of a generator is to change mechanical energy to electrical energy transformers can be a step up transformer or a step down transformer

step up transformers The step up transformer increases voltage Ex. A step-up transformer the number of turns of wire is greater in the secondary coil than in the primary coil, and the output voltage exceeds the input voltage

Alternative Energy Hydroelectricity is electricity generated by falling water Water that flows due to the gravitational forces among Earth, the Moon, and the Sun has tidal energy Devices that use semiconductors to produce electricity from solar energy are photovoltaic cells

Fossil Fuels Three types of Fossil Fuels Petroleum Natural gas Coal Coal is the type of fossil fuel that is formed from the remains of fernlike plants Petroleum is separated into different compounds due to fractional distillation

Fossil Fuels Natural Gas produces fewer pollutants than other fossil fuels Petroleum is make of hydrocarbons Coal contains more impurities than other fossil fuels One of the major reasons for alternative fuels is that fossil fuels are being used at a faster rate than they can form. This is why coal is considered a non renewable source of energy.

Biomass fuels Fuels made from renewable organic matter are referred to as biomass fuels. Wood Rice hulls Corn Sugar cane

Nuclear fuels Fuel generated by nuclear fission The temperature generated by the nuclear reaction is the biggest challenge in using this type of fuel The part of a nuclear reactor in which the fuel is located is the core. In nuclear fusion or in fission matter is converted into energy The fuel used inn a nuclear reactor usually comes from uranium-238. The best hope of safe, long term containment of radioactive waste is deep stable rock deposits.