Electromagnetic Induction

PhysicsTobler

What is electromagnetic induction?

►Voltage can be created by changing the magnetic field within a coil of conducting wire

►Either magnet or conductor can be moving

►In 1831, discovered simultaneously by Faraday in England and Henry in the US

►No voltage source needed!!

James Clark Maxwell

►In the 1860s, Maxwell stated: A changing electric field will create a

magnetic field The magnitude of the magnetic field

depends on how fast the electric field is changing

The induced magnetic field will be at right angles to the electric field

Faraday’s Law

►Voltage depends upon 2 things:# of loops (magnetic field strength)

Rate at which the magnetic field changes (How fast the magnet or coil moves in the field)

Video Clips

►Magnetism in current carrying wire►Force on a current carrying wire►Motor vs generator

Generators

►Move the coil instead of the magnet►Mechanical energy to electrical energy

Opposite of a motor►One complete rotation=one complete

cycle in voltage and current How many cycles/second in US?

►60 cycles/sec

Large Generators►Power plants use much

larger generators►Turbines used to turn the

coil within large magnetic fields

►What is used to turn the turbine? Usually steam, also wind

and water

Transformers►What does a transformer do?

Used to step up or step down voltages►How it works

Consists of an iron core to guide magnetic fields

A/C is sent through the first coil This creates a changing magnetic field This creates a voltage in the second coil

Power Transmission►Using A/C generators and transformers,

power can be transmitted great distances at very high voltages and very low currents

► Low current=low energy loss….Why? High currents would cause the wires to heat

up Loss of heat=loss of energy

►Conservation of energy In the home 120 W=120 V * 1 A Power lines 120 W= 120,000 V * 0.001 A

How transformers are used in Power Grid

Hydroelectric Dam

Hoover Dam Power Plant

Hoover Dam Power Plant

Nuclear Power Plant

Use heat from nuclear reaction to turn the water to steam to turn the turbines to generate the electricity.

Coal Power Plant

Use heat from burning of coal to turn the water to steam to turn the turbines to generate the electricity.

Solar Power PlantUse solar energy to heat water to steam to turn the turbine to generate electricity

Examples of Electromagnetic Induction

►Microphones►Speakers►Motors and generators►Metal Detectors►Traffic lights►Tape recorders and VCRs