Science In Action 9 Unit D Section 3&4

Energy

ability to do work

Chemical Energy

energy stored in chemicals and released when chemicals react; a form of potential or stored energy

Electrical Energy

energy of charged particles; transferred when electrons travel from place to place

Mechanical Energy

energy possessed by an object because of its motion or its potential to move; a thrown baseball has mechanical energy because of its movement and its potential to fall

Thermal Energy

the total kinetic energy of all the particles in a substance; the faster a particle moves, the more kinetic energy it has

Thermocouple

device consisting of two wires of different metals joined such that a voltage is produced between the ends in a proportion to the difference in their temperatures

Electromagnet

coil of insulated wire (usually wrapped around a soft iron core) that becomes a magnet when current flows through it

Commutator

split ring in a motor that breaks the flow of electricity for a moment and then reverses the connection of the coil

Brush

mechanism that makes electrical contact with the moving commutator in a motor

Armature

rotating shaft and coil in a motor or generator

Direct Current

current that flows in only one direction

Alternating Current

current that flows back and forth 60 times per second; this is the current used in homes

Transformer

device that changes electricity at one voltage into electricity at a different voltage

Step-up transformer

increases the voltage

Step-down transformer

decreases the voltage

Electromagnetic Induction

generation of electric current in a conductor by a changing magnetic field

Voltage

a measure of how much electrical energy a charged particle carries

Electromagnetic Induction

generation of electric current in a conductor by changing a magnetic field

Power

rate at which a device converts energy

Power Rating

the amount of power required for a particular device

Energy Consumption

input energy multiplied by the time the device is used; E = P × t

Kilowatt hour

commonly used unit of electrical energy, equal to a power consumption of 1000 W for one hour

Law of Conservation of Energy

fundamental principle that energy cannot be created or destroyed

Efficiency

ratio of the useful energy output to the total energy input in a device or system; usually given as a percent

Factors that limit efficiency

friction causes energy loss by converting some input energy to thermal energy

How can efficiency be increased

decreasing friction; adding more insulation to reduce heat transfer

Energy Sources

Fossil fuel

fuel formed from dead plants and animals; coal, oil and natural gas

Nuclear fission

splitting of atoms, which transforms them into lighter elements and releases large amounts of energy

Geothermal energy

energy derived from the internal heat of the earth

Biomass

organic matter, such as food or agricultural waste, used as an energy source

Hydroelectric power

power is generated by using a dam or diversion structure to alter the natural flow of a river or other body of water

Tidal/ocean

generate electricity by trapping water in reservoirs during high tide, then letting it back out through turbines

Wind

generates electricity by turning large propeller shaft blades connected to a turbine

Solar

energy from the sun that is converted into thermal or electrical energy

Fuel cell

primary cell that generates electricity directly from a chemical reaction with a fuel

Cogeneration

use of waste energy from a process for another purpose, such as heating or generating electricity

Renewable resource

resource such as water or wind energy that is continually replenished and therefore can be used indefinitely

Nonrenewable resource

a resource, such as coal or natural gas, that cannot be replenished

Fly ash

fine airborne ash produced by burning coal or other solid fuels; causes air pollution

Acid rain (Sulfur dioxide)

contributes to air pollution

Nitrogen oxides

major air pollutant; forms when nitrogen combines with oxygen as a result of fuel combustion

Carbon dioxide

cause of global warming, which leads to climate change

Strip mines

soil near the surface is cleared to get to coal deposits; removes all plants and animals from large areas of land

Thermal pollution

when steam turbines release warm water into lakes and rivers; increased water temperature can kill fish

Sustainability

use of resources at a rate that can be maintained indefinitely without depleting the resources or harming the environment

Binary number

number having two as its base (instead of 10) and so having only ones and zeroes