Electricity and magnetism connection

History In 1820 Hans Christian Oersted

discovered electricity passing through a wire created a magnetic field

However the only way to create an electric current at the time was reacting expensive materials (forerunner to a modern battery)

This is completely impractical to provide electricity on a large scale

Discovery A moving magnetic field can also

create and electric current This was discovered separately and

simultaneously by Michael Faraday in Britain and Joseph Henry in America in 1831.

Both moved a coil of wire over a magnet and saw a current was created, and the current created a magnetic field.

Electromagnetic Induction ~ the creation of a magnetic field by

electric current or the creation of an electric current by a magnetic field.

The amount of voltage depends on how quickly either the magnet or wire is moving.

Faster motion means a higher voltage will be created.

Faraday’s Law ~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.

The voltage also depends upon the number of loops it is passing through

Eddy Current Moving a magnetic field through a

conductor shaped in a cylinder. (or vice versa)

causes a circulating flow of current (eddy)

The resistance in the conductor causes a dragging effect (like friction) slowing the magnet down.

These are used as breaking systems at the end of some roller coasters

Eddy Forces

Generators Generators produce electricity by

spinning a coil of wire in front of permanent magnets.

Since it keeps going back and forth it produces an alternating current.

If you want a DC current you have use a commutator (works the same as the stuff in a DC motor)

Alternating Current Remember alternating current

simply sway back and forth They don’t move through (constantly

in one direction) a wire The electrons have a net movement

forward, then backward (repeat) This is why alternating current

generators are called an alternator

GeneratorDC generator in action

AC generator in action

Generators The shaft of the loop of wires is

connected to a turbine. The goal of all electric power plants

is to get a turbine to spin. By spinning this turbine we can

convert mechanical (kinetic) energy to electromagnetic energy.

Types of power plants Hydroelectric- put a turbine in a river

or water fall and let the water spin the turbine.

Coal- burn coal to boil water, steam rises and spins a turbine.

Nuclear- same as coal but use a nuclear fission to boil water.

Hydroplant

Coal Plant

Nuclear power plant

homework Pg 758 1-10