• Targets
• describe how mutual induction occurs in
circuits
• apply the transformer equation to solve
problems involving step up and step down
transformers
• Do Now
• staple and turn in Experiment 20.3 report
• Homework
• read pp. 721, 727-730
• complete Transformer Activity pre-lab
Friday, 5 March 2010
Generator
• a machine that converts mechanical
energy into electrical energy
• ac generator: produces alternating
current (has slip rings)
• dc generator: produces direct current
(has split rings)
Friday, 5 March 2010
Examples of Generators
Friday, 5 March 2010
Examples of Generators
• hydroelectric plant
• wind turbine
• coal-based power plant
• gasoline-powered generator
• car alternator
• hybrid car braking system
Friday, 5 March 2010
Motors
• convert electrical energy to mechanical
energy
• almost identical in constructor to a dc
generator
Friday, 5 March 2010
Transformer
• a device that increases or decreases the
emf of alternating current
• primary coil: connected to emf source
• secondary coil: connected to load
• coils are electrically isolated but share a
magnetic field
Friday, 5 March 2010
Transformer Equation
• ΔV / ΔV = N / N
• ΔV : applied emf in primary
• ΔV : induced emf in secondary
• N : number of turns in primary
• N : number of turns in secondary
P
S
P
S
P
S
Friday, 5 March 2010
P
S
Types of Transformers
• step-up transformer
• secondary has more turns than primary (N > N )
• induced emf in secondary is greater than applied
S
P
emf to primary (ΔVS > ΔVP)
• step-down transformer
• primary has more turns than secondary (N > N )
• applied emf to primary is greater than induced emf
P
in secondary (ΔVP > ΔVS)
Friday, 5 March 2010
S
Examples of Transformers
• power distribution
• power bricks for consumer electronics
• car ignition coil
Friday, 5 March 2010