Energy & Its Impact on Global Society Jerome K. Williams, Ph.D. Saint Leo University Dept. Mathematics & Sciences

Chapter 11: Electromagnetism & Generation Electricity Magnetic Forces & Fields Generation of Electricity Transmission of Electricity Electric Power Plant: A Last Look

Magnetic Forces & Fields A simple magnet acts as if there are two centers of force, called poles, labeled north (N) and south (S) Force between poles varies inversely with distance; like poles repel and unlike poles attract

Magnetic Forces & Fields Single Bar Magnet with Field Lines Two Bar Magnets: Opposite Poles Attract

Magnetic Forces & Fields 1820: Link discovered between electricity and magnetism establishing field of study called “electromagnetism” An electric current creates a magnetic field How can we use this?

Magnetic Forces & Fields A coil of wire with current passing through it acts as a magnet, similar to bar magnet. Coil is called a solenoid and is example of electromagnet Used today in many applications as motors and relays; magnetic field created or removed by closing/opening a switch

Solenoid (Fig. 11.3)

Magnetic Forces & Fields A charged particle will experience a force when moving in a magnetic field This is observed in nature as northern lights (aurora borealis) seen near North Pole

Magnetic Forces & Fields

A current-carrying wire placed in a magnetic field will experience a force causing it to move If wire connected to shaft, useful work is extracted; this device is called electric motor To keep shaft turning, one uses alternating current (AC)

Generation of Electricity If an electric current creates a magnetic field, could a magnetic field create a current?

Generation of Electricity A moving magnet will induce a current in the surrounding wire; the faster the magnet moves, the greater the effect Faraday’s Law of Induction Electric Generators use this principle to work

Generation of Electricity

Transmission of Electricity Transmittal of Electrical Power over large distances is impractical; energy losses lead to very low efficiency Problem is avoided by changing voltage at which electricity is transmitted Principle behind a transformer

Transmission of Electricity

Electric Power Plant: A Last Look

Problems 2, 5