Science 30 Unit C

negatively charged

having more electrons than protons creating an imbalance

positively charged

having fewer electrons than protons creating an imbalance

coulomb

an SI unit for charge; one coulomb is equivalent to the transfer of 6.25×10¹⁸ electrons

conductor

a material in which some of the electrons can move freely, allowing the material to conduct an electric current

electric potential difference

the change in potential energy per unit of charge

volt

the unit for electric potential difference 1V= 1J/C

voltage

another term for electric potential difference

electric field

a property of the space around a source that enables the source charge to exert forces on other charges that enter this region

insulator

a material in which none of the electrons can move freely, preventing the material from being able to conduct an electric current

test body

an observable abject that can experience a force due to the presence of a field

magnetic field

a property of the space around a magnet or an electric current that enables the magnet or electric current to exert forces on other magnets such as compass needles, and electric currents that enter this region

gravitational field

a property of the space around a source mass that enables the source mass to exert forces on other masses that enter this region

field lines

lines that describe the direction of a field by the way they point, and the strength of a field by their density

solar wind

a stream of high-speed, ionized particles ejected from the sun, consisting mainly of electrons, protons and helium nuclei

cosmic rays

a stream of high-speed, ionized particles ejected from the objects beyond the solar system, consisting mainly of atomic nuclei

gravitational field strength

the number of newtons per kilogram a test body will experience at a given location from a source mass

gravitational force

the force exerted on a test body by a gravitational field; calculated by multiplying the mass of the test body by the gravitational field strength

electric field strength

the number of newtons per coulomb that a test body will experience at a given location from a source charge

electric force

the force exerted on a charged test body by an electric field; calculated by ,multiplying the electric field strength by the charge on the test body

grounded

connected to the ground; providing a safe conducting path for stray or excess charges; having zero electric potential energy

electric current

the flow of electric charge from one point to another

electrical energy

the energy made available by the movement of charge

mechanical energy

the energy possessed by an observable object due to motion or its position; the sum of the kinetic energy and potential energy of an object

armature

the section of a motor or generator that rotates, consisting of a coil of wire, rotating shaft, and a commutator (pg 359)

commutator

a part of a motor or generator found on the armature that provides electrical contact, allowing current to flow to the rotating coil

shaft

a part of a motor or generator that supports the coil of the armature, providing an axis for the rotation of the armature

brush

a stationary part of a motor or generator that makes electrical contact with the rotating commutator

direct current (DC)

a flow of charges that does not increase or decrease and flows in a single current

alternating current (AC)

a flow of charges that reverses directions at regular intervals

series connection

a single path available for electric current where the charges flow through one device before passing through to the next

parallel connection

more than one path available for electric current, where the electric current divides, allowing each portion of the current to simultaneous pass through separate devices

voltmeter

an instrument that measures the voltage across two points in a circuit

ammeter

an instrument that measures the voltage across two points in a circuit

resistor

an electronic component that resists the flow of electric current in a circuit

resistance

the ratio of the voltage across a device to the current flowing through it

ohmmeter

an instrument that measures the resistance across two points in a circuit

schematic diagram

a sketch that uses symbols to detail the components of a system such as an electrical circuit (pg374)

power

the rate of doing work or transforming energy

kilowatt-hour

the traditional unit for electrical energy used by utility companies; 1 kWh=3.6MJ

primary coil

the coil to which the input voltage is applied in a transformer

secondary coil

the coil that supplies the output voltage of a transformer

transformer

a device that transforms the AC voltage of one circuit into a different AC voltage for another circuit using separate solid of wire wound around a common iron core

radiation

energy emitted in the form of particles or waves

electromagnetic radiation (EMR)

a wave that consists of a changing electric field and a changing magnetic field travelling at right angles to one another

transverse wave

a wave in which the vibrations are perpendicular to the direction the wave is travelling

cycle

one complete vibration of a wave

wavelength

the distance from a point on one wave to the corresponding point on the next wave; the length of one cycle

frequency

the number of waves passing a point in a second (cycles per second)

hertz (Hz)

the unit for frequency

electromagnetic spectrum

the wide band of different types of electromagnetic radiation ranging from radio waves to gamma rays

radio wave

a type of electromagnetic radiation with a frequency less than 3000 GHz; used primarily for communications

antenna

a transmitter or receiver of electromagnetic energy

extremely low frequency (ELF)

electromagnetic radiation with a frequency between 3 and 300 Hz; emitted from power distribution cables

magnetic resonance imaging (MRI)

a method of obtaining internal images of objects, especially living organisms, by using radio waves and strong magnetic fields

microwaves

a type of electromagnetic radiation with a frequency between 1 GHz and 100 GHz

-used for radar, satellite communications and cooking food

-transmits signals from cell phone towers

infrared

a type of electromagnetic radiation with a frequency between 3.0×10¹¹ Hz and 4.3×10¹⁴ Hz

-increases the vibrations between molecules, resulting in heating effects

-can detect location of living things in the dark

beaming

the communication of data between wireless devices using a beam of infrared light

visible spectrum

the complete range of all colours of light that can be seen by the human eye; ROYGBV

-frequencies range from 4.3×10¹⁴ Hz to 7.5×10¹⁴ Hz

photon

a small bundle of electromagnetic energy

ultraviolet

a type of electromagnetic radiation that is emitted by very hot objects

-sterilizes items

-frequencies range from 7.5×10¹⁴ to 1×10¹⁸

ionizing radiation

high-energy radiation capable of ionizing the material through which it passes, leading to the formation of free radicals

X-rays

high energy electromagnetic radiation with a frequency between 10¹⁸ and 10²¹ Hz; medical diagnostic tool to detect fractured bones

radiation therapy

the medical use of ionizing radiation to treat disease, especially forms of cancer

radioactive

a term used to describe substances that spontaneously emit radiation from unstable nuclei

gamma radiation

the highest ENERGY form of electromagnetic radiation with frequencies above 10¹⁹Hz; emitted from the nuclei of radioactive materials

constellation

a group of stars perceived as being in the shape of a figure or a design

astronomy

the science of objects and phenomena that originate outside earth's atmosphere

nuclear fusion

a process in which two smaller nuclei join to form a larger nucleus, releasing energy

refraction

a bending in the direction of a wave that occurs when the wave changes speed

reflection

a return of a wave from a boundary; bounces off solid objects at the same angle they hit)

polarization

confining a wave to vibrate in one direction

diffraction

the bending of a wave as it passes by obstacles or through small openings

resolution

the amount of small detail visible in an image; low resolution means only large features can be seen, while high resolution means that small details can be seen

false-colour image

an image that depicts an object in colours that differ from how a person would see the same object using only his or her eyes; often used to produce images using EMR outside of the visible spectrum

multi wavelength astronomy

the study of objects in space using the principle that these objects reveal different aspects of their behaviours through the many wavelengths of EMR they emit

diffraction grating

a piece of glass or plastic with thousands of tightly spaced lines etched on its surface; used to produce spectra

continuous spectrum

a spectrum having no distinct lines that is distributed over an unbroken band of wavelengths; produced by hot, incandescent (or glowing) light under HIGH pressure

absorption or dark-line spectrum

a spectrum that has a pattern of dark lines due to the light passing through a cold gas; can be used to identify a material

emission or bright-line spectrum

a spectrum that has a pattern of separate bright lines that is emitted from an excited gas under LOW pressure; can be used to identify a material

spectra

plural form of spectrum (resulting pattern)

-device that allows to observe spectrum is spectroscope

spectrometer

an optical instrument that can measure/detect wavelengths of light being absorbed/emitted

Doppler effect

a change in the observed frequency of a wave due to motion between the source and the observer

blue shift

higher frequency (short waves) due to a source of EMR moving TOWARD an observer, due to the Doppler effect

red shift

lower frequency (long waves) due to a source of EMR moving AWAY from an observer, due to the Doppler effect

red giant

a star of great size and age that has a relatively low surface temperature

nebula

an interstellar cloud of gas and dust (“nursery” for stars)

white dwarf

a compact star found as the last stage in the evolution of low-mass stars

supernova

a stellar explosion that produces a very bright cloud of ionized gas that remains a very bright object in the sky for weeks or months

neutron star

a super-dense star consisting mainly of neutrons formed as the last stage in the stellar evolution of intermediate-mass stars

pulsar

a rotating neutron star that emts radiation in regular pulses

black hole

collapse of high mass stars concentrates the gravitational field and not allow light ot be emitted