CITE: quiz 6

Dr. Bader Power Grid

dynamic energy

also called electric current and is the uniform motion of electrons through a conductor

conductor

a substance in which the outer electrons in the atoms can move around freely (metals are good conductors)

circuit

a complete, unbroken pathway for electrons to move continuously in and out of the conductor

voltage can be represented by?

the pressure in a water tank forcing water through the pipe

current can be represented by?

the water flowing through the pipe represents the electrical current and the more pressure there is the more current you get

voltage

the amount of potential energy available to move electrons through a conductor between two points

current

when a voltage source is connected to a circuit, the voltage will cause a uniform flow of electrons through the circuit

what are the sources of generating voltage?

chemical reactions (batteries), radiant energy (solar cells), and the influence of magnetism on conductors (generators)

resistance

the measure of opposition to electric current

resistance is caused by?

voltage sources, properties of conducting materials, and the object receiving the electron (i.e. resistor)

ohm’s law

the amount of electric current through a metal conductor in a circuit is directly proportional to the voltage (VIR)

what is VIR?

V = voltage, I = current, R = resistance

power (work)

power equals the flow rate times the potential and is measured in “watts”

circuits AC and DC?

describe the types of current flow in a circuit

direct current (DC)

the electric charge (current only flows in one direction) and most electrons use DC as they need batteries; provides a constant voltage

what current voltage is lower?

DC is normally lower than AC

what are the three methods for connecting power sources for DC current?

single, series, and parallel

what is a single connecting power source (DC)?

minimum amount of components to be a functional circuit: source (battery), resistor, loop of wires

what is a series connecting power source (DC)?

one path for current flow, so each component'/resistor of the circuit has to share the current

the total voltage equals the?

sum of all voltages

what is a parallel connecting power source (DC)?

total current equals the sum of individual branch currents

the same voltage across every component in the circuit is the same as?

total voltage

alternating current (AC)

the current changes direction periodically

most homes are wired for which current?

AC (plug in)

what are the useful properties of AC?

they are able to convert voltage levels with a transformer

which current was chosen as the primary means to transmit electricity over long distances?

AC

ampere (amps)

the “rate” that current is flowing through the circuit; also the number of electrons moving through the conductor

the larger the amps, the more?

electricity that can flow through the circuit

large appliances are usually ___ amp while outlets are usually ___ amp circuits

30; 15-20

when was the first modern use of electricity?

1880

parts of the US did not get electrical power until the?

1930’s

base load

minimum electricity required in a 24 hour period (mostly coal and nuclear)

peak

daily fluctuations

large power plants

improve efficiency of converting fuel to electricity and reduce pollution from power generation

transmission

power has to travel long distances

what are the two major issues of the power grid?

generation and transmission

what is the main issue with generation?

the type of fuel and location

who has the most polluted cities in the US?

california

who has the most polluted cities in the world?

china

transmission affects?

cost, reliability, safety, and environmental impacts

moving magnetic fields do what to electrons?

push and pull them like a magnet

metals like copper do not hold tightly to?

their electrons

electrical generators basically convert the mechanical energy into?

electrical energy

the resistance of the wire is equal to the?

voltage over the current (R=V/I)

when you try to pass an electron flow through the wire

the voltage helps you, the resistance limits you, the higher the voltage, the higher the current, and the higher the resistance, the lower the current

induce

to cause or bring about

inductor

a coil of wire wrapped around an iron core that creates a magnetic field

self inductance is when

the current in the coil wire changes, the magnetic field also changes, the magnetic field created by the current grows or shrinks depending on whether the current increases or decreases, if the current stays steady then no inductance occurs

transmission mutual inductance

when two or more coils of wire are in proximity around the same iron core

in transmission, the voltage can be?

stepped up or stepped down at any point

what are the direct problems with AC current?

how much power you can send, minimum spacing between lines, how much of the grid can be buried, lines above the surface and transformers can be damaged by weather/objects, stray currents can be created that harm farm animals or humans

what are the indirect problems with AC current?

power generation must be carefully monitored, ensure all generators are in phase with each other, damage the power plants and/or transmission lines can occur, humans and most animals run on AC, AC at almost any voltage and current can be dangerous, danger increases with both but mostly with current

what are some problems with high voltage?

locally change the earth’s magnetic field, cause problems for human navigation aids, disturbs migration patterns of animals, may cause some forms of cancer

what are things that can go wrong with transmission?

lines can fail, transformers can fail, switching equipment can fail, chain reaction failures

what are the 4 enemies of the power grid?

nature, wars and attacks, economic issues, and operators