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SALT 9th - Chp 15-16
SALT 9th Science - Chp 15-16
| Question | Answer |
|---|---|
| electrostatics | the study of the nature, behavior, and uses of static electricity and related phenomena |
| electric charge | always moves to the outside of the charged object |
| electron | possesses a negative charge |
| proton | possesses a positive charge |
| neutral | an atom or other object that has no overall electrical charge |
| electric field | the region surrounding a charged object in which other objects are attracted or repelled by an electric force |
| coulomb | the unit of electric charge |
| law of electric charges | opposite charges attract, but like charges repel |
| Coulomb’s law of electric force | states that the strength of the attraction or repulsion between two charged objects is directly related to the strength of the charges and inversely related to the square of the distance between them |
| grounding | the process of diverting unwanted electrical charge directly into the earth |
| contact | electric charge can be transferred between object by direct contact, which is not temporary |
| induction | electric charge can be imparted at a distance, without direct contact between the charged object and the uncharged object, charging by induction is usually temporary |
| electroscope | simple device that uses the laws of electrostatics to detect small electric charges |
| Van de Graaff generator | device used to produce static electricity |
| lightning rod | device for protecting buildings and other structures from lightning strikes |
| Leyden jar | early device used to store an electric charge |
| capacitor | a modern device used to store electrical charges, such as in some camera flashes and other electronic devices |
| magnet | object capable of attracting objects such as iron or steel |
| lodestone | the Vikings were guided in their journeys across the North Atlantic by these unusual magnetic rocks |
| law of magnetic poles | unlike poles attract, but like poles repel |
| north magnetic pole | It is magnetically an S-pole. |
| law of magnetic force | the force between two magnetic poles is directly related to the product of the pole strengths and inversely related to the square of the distance between the poles |
| magnetic compass | navigational device consisting of a magnet free to swing horizontally |
| dipping needle | compass that swings vertically to reveal the angle at which lines of force enter the earth |
| electromagnet | device that produces a strong magnetic field when electricity passes through it |
| magnetic equator | an imaginary circle around the earth halfway between the two magnetic poles |
| Van Allen radiation belts | the two vast, doughnut-shaped belts of high-speed particles trapped in the earth’s magnetic field |
| domain theory | the magnetic field of a magnet is the sum of thousands of smaller fields, each produced by billions of atoms containing unpaired, spinning electrons |
| diamagnetic | a material that is slightly repelled by either pole of a magnet and that has no unpaired electrons per atom |
| paramagnetic | a material that is weakly attracted to magnets and that has only one unpaired electron per atom |
| ferromagnetic | a material that is strongly attracted to magnets and that has several unpaired electrons per atom |
| temporary magnet | made from magnetically “soft” material, it quickly loses most magnetism when the magnetic field is removed |
| permanent magnets | made from magnetically “hard” material, they retain their magnetism for a very long time. |
| magnetization methods | by contact, by electricity, by induction |
| current electricity | the “flow” of electrons from one place to another |
| volt | the unit used to measure the force with which an electric current flows |
| ampere | the unit of electron current |
| watt | the SI unit of power |
| ammeter | instrument used to measure amperage |
| kilowatt-hour | the unit used by electric companies to charge for electricity |
| conductors | materials through which current flows easily |
| insulators | materials through which current does not easily flow |
| semiconductors | materials that are neither good conductors nor good insulators |
| resistance | the amount a certain object or material hinders electron flow |
| ohm | the unit used for measuring resistance |
| superconductor | a material that allows electric current to flow through it with not resistance at all |
| Ohm’s law | current (amperage) in a conductor is directly proportional to voltage and inversely proportional to resistance |
| closed circuit | a circuit that contains a complete path for electrons to flow from the source of current, through the load, and back to the source |
| open circuit | a circuit that contains a gap which electrons cannot cross |
| switch | device used to manually open or close a circuit |
| circuit breaker | automatic switch that opens the circuit when current flowing through it exceeds a predetermined amount |
| fuse | a narrow strip of metal in a protective insulated case, used to stop the flow of electricity when a short circuit or overload occurs |
| parallel circuit | a circuit with loads arranged in separate branches of the circuit so that the current is divided among them |
| series circuit | a circuit with loads arranged so that the electric current flows through each load one after another |
| fluorescent lamp | an electric discharge lamp which produces light by passing an electric current through a long tube filled with mercury vapor at low pressure, causing a coating on the inside of the tube to glow |
| telegraph | device for communicating over long distances by means of electromagnets |
| loudspeaker | device that converts pulses of electricity into sound waves |
| electric motor | device that converts electricity into motion |
| storage cells | devices that produce electric current and are designed to be recharged when they “run dry” |
| voltaic cells | devices that produce electric current but are not designed to be recharged |
| battery | a group of electrochemical cells connected together as a single source of current |
| generator | device that uses electromagnetic induction to produce electric current |
| transformer | device that increases or decreases the voltage of alternating current by means of electromagnetic induction |
| Explain the close relationship between magnetism and electricity. | Both magnetism and electricity are manifestations of the electromagnetic force. |
| How can electricity produce magnetism, and magnetism produce electricity? | When an electric current flows through a wire, it generates a magnetic field around the wire, forming an electromagnet.When a conductor “cuts” the lines of force in a magnetic field, it generates an electric current |
| When does a short circuit occur? | When electricity is given the opportunity ot take a “short cut” through a circuit, avoiding the load |
| What is the angle that a compass needle deviates from the true north called? | the angle of declination |
| List the three main components of a simple electric circuit | source of current, conductors, load |
| Why are electric charges commonly called static electricity? | When an object is electrically charged, its electrons tend to “stay put” (remain stationary) on the surface of the charged object (the word “static“ means ”stationary”) |
| What is solar wind? | A stream of protons and electrons that emanate from the sun |
| How does current electricity differ from static electricity? | In current electricity, the electrons “flow” from one place to another.In static electricity, the electrons remain in one place. They are stationary. |
| What are two types of electric current? | direct current (DC), alternating current (AC) |