Devices to prevent excessive currents Fuses Current flows through thin metal piece with low melting temperature Too much current &reg; the heat produced by resistance melts the fuse, which breaks the circuit Circuit breakers Two designs: Magnetic field due to a current in a coil of wire Resistive heating of a bimetallic strip When the current is large enough, the strength of the magnetic field of the coil is enough to open a mechanical switch Circuit breakers Series and parallel circuits Cost of energy production Cost depends on amount of use cost of construction cost of fuel Base -- nuclear, hydroelectric Cycling -- coal Peak -- gas Reserve should be 20% greater than peak Monopoly Economy of scale smooth out demand by averaging, and by recruiting industrial customers with lower prices difficulty of storing electrical energy regulated by PUC s, guaranteed profit today: deregulation Decentralized model Renewable diverse sources flexible, low tech scaled to use match in quality e.g., heat directly, don t convert to electric More about decentralization Cogeneration e.g. electricity from waste heat of paper mill "total energy" e.g. local trash burner (but inefficient, because of low temperature;
(Devices; to prevent; excessive currents Fuses) (the heat; produced; by resistance melts) (the heat produced by resistance melts the fuse; breaks; the circuit Circuit breakers) (electrical energy; regulated; by PUC s) (the current; is; large enough)
Devices the heat the heat produced by resistance melts the fuse electrical energy the current
to prevent produced breaks regulated is
excessive currents Fuses
by resistance melts
the circuit Circuit breakers
by PUC s
large enough