Electricity & Magnetism An electric current in a wire creates a magnetic field. [

[ demos/797Solenoid_and_iron_filings.jpg] Click here to view demonstration videos.

Electricity & Magnetism Conversely, a moving magnet can create an electric current in a wire. Click Here for a Demo

Electric Generators Motion is turned into Electricity A “force” spins a loop of wire inside a magnet producing electric current This occurs because of electromagnetic induction [ 05/turbine_001_diagram.jpg]

Electric Generators Generators normally produce Alternating Current (AC) which changes the direction that electrons move. (120 times per second) Batteries produce Direct Current (DC) where electrons always move the same direction. Click Here for an Interactive Example

Electromagnets Piece of iron placed inside a loop of copper wire. Magnetic field is present only when current is flowing in the wire. [

S NS N Magnetic poles reverse when current is switched.

[ Click Here for Speaker Demo

Electric Motors Electricity is turned into motion. Current is passed through an electromagnet so it turns inside a “normal” magnet to produce motion. Click Here for Demos c_motor_cycle_2.png/300px-Electric_motor_cycle_2.png

Electric Motors For DC motors, the commutator switches the current in the electromagnet.

Transformers These change the voltage of alternating current. Click Here for an Interactive Demo

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[ Voltage is controlled by the coils of wire at the ends. Power is the same V in V out

[ V in V out

Transformers Example:Example: What does the voltage change to in the transformer below?What does the voltage change to in the transformer below? [ V in = 50 V I in = 10 A V out = ? I out = 2.5 A

[ V in = 50 V I in = 10 A V out = ? I out = 2.5 A First, calculate the power on the primary side… P = V x I P = 50 V x 10 A P = 500 W

[ V in = 50 V I in = 10 A V out = ? I out = 2.5 A Power is equal on both sides, so use the power to calculate V out… 500 W = V x 2.5 A 2.5 A V = 200 V