Physics Work Definitions

electrical heating system

a system that uses electricity to produce thermal energy for heating

forced-air heating system

a system that moves hot air to heat a building

hot water heating system

a system that uses hot water to heat a building

geothermal system

a system that transfers thermal energy from under Earth's surface into a building to heat it, and transfers thermal energy from the building into the ground to cool the building

proton

a positively charged particle in the nucleus of an atom

neutron

an uncharged particle in the nucleus of an atom

nucleons

particles in the nucleus of an atom; protons and neutrons

electron

a negatively charged particle found in the space surrounding the nucleus of an atom

ground state

state in which all electrons are at their lowest possible energy levels

excited state

state in which one or more electrons are at higher energy levels than in the ground state

isotope

a form of an element that has the same atomic number, but a different mass number than all other forms of that element

radioisotope

an unstable isotope that spontaneously changes its nuclear structure and releases energy in the form of radiation

radiation

energy released when the nucleus of an unstable isotope undergoes a change in structure

radioactivity

a process by which the nucleus of an atom spontaneously disintegrates

nuclear fission

the decomposition of large, unstable nuclei into smaller, more stable nuclei

nuclear reaction

the process by which the nucleus of an atom sometimes changes

electrostatic force

the force of attraction or repulsion due to electric charges

strong nuclear force

the very strong force of attraction between nucleons

radioactive decay

the process by which a radioactive atom's nucleus breaks apart and forms different atoms

alpha decay

nuclear reaction in which an alpha particle is emitted

alpha particle

a particle emitted during alpha decay; composed of a helium nucleus containing two protons and two neutrons

parent atom

the reactant atom in a nuclear reaction

daughter atom

the product atom in a nuclear reaction

transmutation

a nuclear decay process in which daughter atoms are different elements from parent atoms

beta decay

nuclear reaction in which a beta particle is emitted or captured

beta particle

a high-energy electron or positron ejected or captured by a nucleus during beta decay

positron

a particle with a positive charge and the same mass as an electron

photon

a high-energy particle with no mass

gamma decay

a reaction in which an excited nucleus returns to a lower, more stable energy state, releasing a very high-energy gamma ray in the process.

half-life

the average length of time it takes radioactive material to decay to half of its original mass

atomic mass unit

a unit of mass equal to 1.66 x 10^(-27) kg

mega-electron volt

the energy required to accelerate an electron through a potential difference of 1 million volts; 1.602x10^(-13) J

chain reaction

the repeated series of reactions in which the products of one reaction generate subsequent reactions

calandria

core of the reactor, consisting of fuel bundles, control rods, and moderator

fuel bundles

fuel elements consisting of uranium pellets

control rods

adjustable cadmium rods used to control nuclear reaction rates

moderator

heavy water used to slow neutrons and absorb thermal energy

steam generator

absorbs thermal energy from the heavy water in the primary loop, producing steam

primary loop

closed loop through which heavy water flows

secondary loop

closed loop through which normal water, which becomes steam, flows

Energy resource

energy-rich substances

non-renewable energy source

a substance that cannot be replenished as it is used in energy-transforming processes

renewable energy resource

a substance with an unlimited supply or a supply that can be replenished as the substance is used in energy-transforming processes

fossil fuel

fuel produced by the decayed and compressed remains of plants that lived hundreds of millions of years ago

nuclear fusion

a nuclear reaction in which the nuclei of two atoms fuse together to form a larger nucleus

solar energy

radiant energy from the sun

passive solar design

building design that uses the sun's radiant energy directly for heating

photovoltaic cell

a device that transforms radiant energy into electrical energy

hydroelectricity

electricity produced by transforming the kinetic energy of rushing water into electrical energy

geothermal

- thermal energy from deep underground; can be used directly or transformed into electrical energy
- accessible only in certain areas
- in some locations, deep holes need to be drilled into the ground to reach pockets of thermal energy

wind

- wind strikes the blades of a turbine, which turns an electricity generator that generates electrical energy
- can only be used in windy locations
- turbines are noisy, and the blades may strike birds and other wildlife

tidal

- energy generated from the rise and fall of tides/movement of water
- may disrupt aquatic ecosystems

biofuels

- solid, liquid, and gaseous fuels derived from the bodies of living or dead plants and animals
- can include wood, biological waste, and gases such as methane produced during the decomposition of plant matter
- burning fuels may produce air pollutants; including carbon dioxide, which is linked to climate change

work

a transfer of mechanical energy (scalar; measured in joules)

joule

a unit of measurement of work and energy, equivalent to a newton times a metre

energy

the capacity to do work (scalar; measured in joules)

gravitational potential energy

the energy possessed by an object because of its position relative to a lower or higher position

kinetic energy

the energy possessed by an object due to its motion

power

the amount of energy transferred or converted per unit of time (scalar; measured in watts)

watt

unit of measurement of power, equivalent to a joule divided by one second

efficiency

the percentage of energy remaining after the energy transformation

gasoline-powered vehicle

- transforms chemical to kinetic energy
- wastes thermal energy
- 8-15% efficient
- produces carbon dioxide, which contributes to climate change
- creates air pollution

electric vehicle

- transforms electrical to kinetic energy
- wastes thermal energy
24-45% efficient
- currently more expensive than gasoline vehicles
more efficient than gasoline vehicles but uses heavy batters that must be constructed and discarded in special ways to limit environmental contamination

bicycle

- transforms kinetic energy from the pedal to kinetic energy in motion
- wastes thermal energy
90% efficient
- most efficient self powered vehicle
- weather dependent
- road safety issues

loudspeakers

- transforms electrical to sound energy
- wastes thermal energy
- 1% efficient
- efficiency seems low, but useful output energy is more than enough to produce audible sound
- most of electrical input is transformed into thermal energy

electric heater

- transforms electrical to thermal energy
- wastes radiant energy
- 98% efficient
- very efficient transformer of electrical energy into thermal energy

hydroelectric power plant

- transforms kinetic to electrical energy
- wastes thermal energy
- 80% efficient
- efficient method of generating electricity
- damming rivers may flood land and disrupt ecosystems

nuclear power plant

- transforms nuclear to electrical energy
- wastes thermal energy
- 30-40% efficient
- relatively efficient for generating electricity
- produces radioactive waste

solar cell

- transforms radiant to electrical energy
- wastes thermal energy
- 20-40% efficient
- relatively efficient for generating electricity

photosynthesis

- transforms radiant to chemical energy
- wastes thermal energy
- 5% efficient
- although it seems relatively inefficient, its the only process that transforms radiant energy into chemical energy in organisms
- directly or indirectly responsible for maintaining virtually all life on Earth

animal muscles (including human muscles)

- transforms chemical to kinetic energy
- wastes thermal energy
- 20% efficient
- although it seems to be relatively inefficient, this energy-transforming process provides all the energy animals use to perform work

thermal energy

the kinetic energy of the atom plus the energy between the attraction of the atom; the total quantity of kinetic and potential energy possessed by the atoms or molecules of a substance

temperature

measure of the kinetic energy of atom

heat

the transfer of thermal energy

conduction

process of transferring heat by particle collision

convection

process of transferring heat by a circulating path of fluid

radiation

process of transferring heat through a wave form of electromagnetic radiant energy

bad conductors of heat

wood, plastic

good conductor of heat

metal

specific heat capacity (c)

the amount of energy (heat) required to raise the temperature of 1kg of a substance by 1 degree celsius; measured in joules per kg times celsius

kinetic molecular theory

- all matter is made up of moving particles
- each atom or molecule exert forces (attraction and repulsion) on each other
- strength of force determines the overall state of the object

latent heat

the amount of thermal energy absorbed or released during a change of state

latent heat of fusion

the amount of thermal energy needed to melt or released to freeze an object; measured in joules

latent heat of vaporization

the amount of thermal energy needed of vaporize or released to condense an object; measured in joules

specific latent heat of fusion

the thermal energy required for 1kg of a substance to melt or freeze; measured in J/kg

specific latent heat of vaporization

the thermal energy required for 1kg of a substance to vaporize or condense; measured in J/kg

celsius scale

the temperature scale based on the boiling point and freezing point of water

fahrenheit scale

the temperature scale based on the boiling point and freezing point of brine

kelvin scale

the temperature scale developed using absolute zero as the point at which there is virtually no motion in the particles of a substance

convection current

a current that occurs when a fluid is continuously heated; caused by warmer, less dense fluid being constantly pushed upward as colder, denser fluid falls downward