Review
Where do we go from here?
Outline
•	Summary of the Physics of Energy.
•	What you need to know for the exam.
The Physics of Energy
•	Energy is the ability to create CHANGE.
–	Change is acceleration -- KINETIC energy 
–	Change is change of position -- POTENTIAL energy.
•	Energy is associated with the action of some FORCE.
•	Energy is transferred either by doing WORK or by HEATING.
•	Energy is CONSERVED, it is neither created nor destroyed, only exchanged. 
Using Heat to do Work
•	Heat is a form of energy
•	The introduction of heat causes temperature to rise.
•	Most objects expand at higher temperature.
•	Expansion of gases or liquids can be made to do work.
Heat Engines
•	Heat Engines operate in cycles
•	In one cycle, WORK DONE = NET HEAT EXTRACTED.
–	The First Law of Thermodynamics
•	All heat engines EXHAUST HEAT at a lower temperature.
•	Efficiency is the ratio of WORK to HEAT INPUT.
•	The maximum efficiency is 1 – Tc / Th.
–	The Second Law of Thermodynamics
Electrical Power
•	Electric Potential is the amount of energy stored per Coulomb of separated charge.
•	Electrical current is the flow of electrical charge and energy through a circuit.
•	Electrical Power is P = V I, the rate of energy flow, measured in watts.
Magnetic induction of electricity
•	Faraday’s law: A changing magnetic field through a closed conducting loop produces an electric current.
•	Rotating a wire loop in a magnetic field produces an AC or DC current – an electric generator.
•	Sending an AC or DC current through a loop in a magnetic field makes the loop rotate – an electric motor. 
Electricity Transmission
•	Ohm’s law: V = I R. 
–	An electric potential produces an electric current in proportion to the resistance R.
•	Power loss: P loss = I2 R.  
–	All circuits lose power to Joule heating at a rate proportional to R and the current squared.
•	Transformer Law: I af = (V bef / V af ) I bef 
–	Step—up transformers decrease the current by x –times to reduce power loss by x2 times.

Power Plant 
Power Plant, continued
Studying for the test
•	Know the Physical Laws
•	Know the symbols, the definitions of the quantities and the units.
•	Review the homework questions
•	Review the readings and class notes.