# Physics 7 Study Guide- Magnetism and Electricity Physical Science

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What is a solenoid?

By looping wire, magnetic fields of the wire are layered, creating a strong magnetic field within the \”loops\” magnetic field produced by a current can be turned on or off- turn current on or off have its direction reversed- reverse current direction have its strength changed- wires bent into loop inside wire, bunches up magnetic field lines, two loops makes it twice as greater: more loops or coils, stronger magnetic field A coil of wire with a current: two ends act like magnetic poles north and south poles change with direction of current
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What does a motor do and briefly describe how it works?

Magnets cause a wire with electricity to spin transforms electrical energy into mechanical energy uses an electric current to turn an axle Two magnets are placed on each side of a looped wire A current is sent through the wire The wire becomes magnetic The magnet and magnetic wire repel and the wire makes a half turn The electric flow of the wire is reversed, switching its magnetism to cause another half turn- finishing the rotation The process repeats itself The spinning action powers a machine
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What does a generator do and briefly describe how it works?

Wire spinning between magnets makes electricity a device that transforms mechanical energy into electrical energy (opposite of electric motor) instead of using an electric current in a magnetic field to produce motion, it uses motion in a magnetic field to produce an electric current Reverse design of a motor A force of nature (wind, fire, water falling) spins a looped wire The magnets force the electrons within the wire to move with each revolution of the wire The electrons move along the wire in the form of electricity to an appliance
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What does it mean to have an alternating current (AC)?

The electric flow goes back and forth the wire in the magnetic field is moved up and down repeatedly (producing AC) consists of charges that move back and forth in a circuit can be easily raised or lowered to a higher or lower voltage
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What is the difference between AC and DC?

In AC, the electric flow goes back and forth better for power plants the wire in the magnetic field is moved up and down repeatedly consists of charges that move back and forth in a circuit can be easily raised or lowered to a higher or lower voltage In DC, the current moves only in one direction used in batteries DC can be induced from a changing magnetic field or produced from an energy source such as a battery.
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Why do power plants produce AC power?

This is because AC is used in homes, schools, and other buildings (making it easier to power them) The power plants can easily raise or lower the voltage, meaning that a high voltage can be sent over great distances and then reduced to a safer level for everyday use. This is the basic job of a power plant, and AC compliments that.
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What are the different resources used to power generators?

Most power ultimately is produced by a fusion Energy resources: Wind Rivers Ocean currents Fossil Fuels Nuclear plants Solar Energy Geothermal Energy
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What is a benefit of using renewable energy sources over nonrenewable energy sources?

Renewable energy sources can be naturally and quickly replaced, while nonrenewable energy sources only exist in a limited amount.
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What is an electric circuit?

An electrical device that provides a \”circular\” path for electric current to flow a complete, unbroken path through which electric charges can flow
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Conductors

conduction- when charges move when objects touch metals such as silver, copper, aluminum are good conductors a material through which charge can flow easily atoms contain electrons that are bound loosely and are able to move throughout the conductor and produce an electric current as they flow through a conductor used to carry electric charge light flips on so fast because electrons are already present inside of your conductors that make up the circuit flip the switch: electrons at one end of wire and pulled while those on the other end are pushed, causing a continous flow of electrons through all parts of the circuit as soon as the circuit is complete
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Insulators

induction- charge is produced without touch charges can not flow easily in these materials electrons in an insulator are bound tightly to their atoms and do not move easily. rubber, glass, sand, plastic, and wood are good insulators used to stop the flow of charges rubber coating of an appliance cord cord carries charges from an electrical outlet to an appliance why no shock when touch cord? Ineer wire is a conductor for the current, rubber coating is insulator cord allows charge to continue to flow, but stops it from flowing into your hands and shocking you.
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What is static electricity and how does one get it?

An electrical charge from a buildup of electrons due to friction between two different materials protons are bound tightly in the center of an atom, but electrons can sometimes leave their atoms. in materials such as silver, gold, copper, and aluminum some electrons are held loosely by their atoms and can move to other atoms loose electron- more protons than electrons- positive charge gain electron- more electrons than protons- negative charge buildup of charges on an object charges build up on an object, but they do not flow continuously. you can get static electricity through: charge by friction- when two uncharged objects rub together, some electrons from one object can move onto the other object. gain- neg loose- pos charge by conduction- charged object touches another object, electrons can be transferred between the two. electrons transfer from obj. with more neg charge to the one with more pos charge charge by induction- objects do not touch when charges transger. the movement of electrons to one part of an object that is caused by the electric field of a second object. electric field around charged object attracts or repels electrons in the second
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How does lightning occur?

Through static discharge when a negatively charged object and a positively charged object are brought together, electrons transfer until both objects have the same charge. the loss of static electricity as electric charges transfer from one object to another is called static discharge. often times producing a spark as electrons transfer between objects they heat the air around they travel until it glows. glowing air is spark lightning is a dramatic example of static discharge during thunderstorms, air swirls violently water droplets within the clouds become electrically charged causing the bottoms of clouds to become negatively charged, inducing a positive charge on the earth below. Electrons jump between the cloud and Earth’s surface, producing a giant spark as it travels through the air. possible because of the charging by conduction
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What is voltage?

the difference in charge between two parts of a circuit (measured in volts) increasing the difference between the two points, increases the push on electrons voltage causes a current in an electric circuit
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How does one calculate voltage?

voltage= current x resistance
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What is an ampere?

Unit for the flow of electric current (named after Andrew-Marie Ampere)
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What is resistance and what factors contribute to it?

resistance is things that slow the current the measure of how difficult it is for charges to flow through a material greater the resistance, the less current there is for a given voltage measured in ohms (Î©) determining factors: Thickness- thin- more resistance Length- longer more resistance Type of material- insulators have high Î© due to fact that difficult for charges to move resistance= voltage/current
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what are the differences between a series circuit and a parallel circuit?

series- only one path for a current to take If any part of the circuit is broken, the current stops the current diminishes as resistance adds with each added object all parts of an electric circuit are connected one after another along one path parallel circuit- several paths for a current to take If one part of the circuit is broken, the current can take alternate routes more paths, more current (amps) across the whole circuit= bright light bulbs
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short circuit

the current takes an unintended path a connection that allows current to take the path of least resistance. flow through person rather than wire to the power plant (lessÎ©) current can be very high and fatal
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what does it mean to have something grounded?

allows current to flow directly to ground if short circuit occurs provides alternate path for electric current a wire that connectd all the electric circuits to the ground or Earth circuit is electrically grounded when charges are able to flow directly from the circuit into the event of a short circuit can use a third prong or plug: two flat prongs of a plug connect an appliance to the household circuit: third prong, round, connects any metal pieces of the appliance to the ground wire of the building.
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Compare and contract a fuse and a circuit breaker

fuse: sections of wire that melts and breaks at a given current switch that turns off at a given current contains thin strip of metal that will melt if their is too much current through it. upon melting, it breaks the circuit which stops current found in cars and older buildings must be replaced upon burning out both prevent circuits from overheating circuit breaker: doesn’t need to be replaced and used in newer buildings reusable safety switch that breaks the circuit when the current gets too high. in some, a small metal band heats up and bends away from wires in the circuit disrupting current easy to reset, only pull switch back and reconnect metal band to wires
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What is a Watt?

unit of power to measure how fast an appliance converts electricity into another form of energy . power- voltage x current . watts (p)- Volts (v) x Amps ( I )
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Difference between energy and power

The amount of time you use the power from an appliance
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what unit is power measured in?