Electrical Power
Its production, transformation and transmission
Outline
•	Electric and Magnetic Fields.
•	Electrical generators
•	AC and DC
•	Electric generators in steam power plants.
•	Electricity transmission
•	Transformers
•	Superconductors
•	Electrical motors
Electric and Magnetic Fields
•	Electric and Magnetic forces act “at a distance”.
•	Demonstrations:
•	Van de Graaf generator lighting a fluorescent bulb
•	Iron filings lining up along a magnet.

Fields – Forces affecting space
•	Gravitational fields are strong enough to curve space and change the path of light.
•	Electric fields can break down the atoms in air to make a spark.
•	Magnetic fields protect the earth from cosmic rays and help create the aurora borealis.
Fields – a definition
•	A force field is a map of the space surrounding a mass, charge, or magnet telling you how much force there would be at each point in space if another mass, charge or magnet were there.
•	Demonstration and pictures.

Faraday’s Law
•	If a closed wire loop “sees” a changing magnetic field, a current will be set up in that loop.
•	The field might be changing because the magnet is moving.
•	The field might be changing because the loop is moving in a field that varies in space.
Electric Generator
AC and DC
•	DC = Direct current. 
•	Produced from constant voltage power supplies, such as batteries, fuel cells, etc.
•	The flow of current does not vary with time and moves in ONE direction.
•	AC = Alternating Current.  
•	Produced from electrical generators.
•	The current flows back and forth in the circuit at a rate of 50 or 60 cycles a second.

An Electric Power Plant
Electricity Distribution
•	Power plant efficiency has risen from 8 to almost 40%.
•	To increase efficiency, the plants are huge, producing 1 Billion watts (A gigawatt) of power or more.
•	Efficient electricity distribution becomes key.
•	Thomas Edison preferred DC electricity, Nikola Tesla preferred AC.  Tesla won the argument.
Transformers
The reason why all electricity distributed in America and around the world is AC is simple: Transformers.
•	Transformers change the voltage and current in an AC electric circuit.
•	Step-up transformers increase the voltage and decrease the current.
•	Step-down transformers decrease the voltage and increase the current.

The Transformer law.
•	Transformers cannot create energy.  
•	The power in the circuit after going through the transformer must be the same or less than it was before.
•	So, the transformer law is:
•	V before I before = V after I after.
•	OR:  I after = (V before / V after ) I before 
•	Example:  A step up transformer changes 120 V to 120,000 V.  If the current was I = 20 A, what is it now?
•	I after = (120 V / 120,000 V) x 20 A = .02 A.
Get that current down!
•	Remember: Power lost = I2 R
•	By stepping up the voltage, I reduce the current (e.g. a thousand times, from 20 A to .02 A).
•	By reducing the current by a thousand, I reduce the power loss by a thousand squared, or a million times less power loss.
•	The rule is, when I step up the voltage x times, I step down the current x times.  Then power loss is reduced by x 2 times.

An efficient electricity distribution system
Electric Motors
•	An electric motor is an electric generator in reverse.
•	A current is run through a loop of wire, creating a magnetic field.  
•	The loop is surrounded by a permanent magnet which puts a force on the “magnetic” loop, causing it to turn.
•	By using AC current, you can construct the motor so that the magnet is always causing the loop to turn in the same direction.
•	Demonstration: