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Electricity and Magnetism Chapter 7 Section 1 Chapter 8 Sections 2 & 3 Chapter 7 Section 1 Electric Charge Positive and Negative Charge Atoms have particles ___________________, neutrons, and ___________________ p+ = _____ charge no = no charge e- = ______ charge Same # of p+ and _______ = atoms are electrically neutral Transferring Charge Some electrons are bound _____________ to some objects e- bound to ______________ more than carpet Shoe _______________ e- = - charged Carpet _____________ e- = + charged Static Electricity: accumulation of _________ electric charge Conservation of Charge Def: charge can be _________________ from object to object, but it cannot be _______________ or destroyed. Charges Exert Forces Clingy clothes from a dryer Opposites _________ Force depends on _________________ and size of charge Positive clothes like ________________ clothes Like charges repel Opposite charges attract Like charges repel Electric vs. Gravitational Force ________________ force from p+ and e- in H atom is 1039 times stronger than _________________________ force Most things gravity force is stronger than electrical Conductors and Insulators Conductor: material where e- move ____________________ Metals best conductors – _____________ ____________________ material where e- do NOT move easily Plastics, wood, rubber, ______________ Charging Objects Rubbing materials can ______________ e- - one is (+) the other is (-) charging by ______________ Charge by Induction Def: rearrangement of __________________ on neutral object by nearby charged object. Lightning Static ________________: transfer of charge because of a ________________ of static electricity Clouds have __________________ of air and rain areas of + and – charge build Lightning is _________________ between cloud and ground Thunder Lightning ___________ e- from atmosphere and produces heat increase __________________ Atoms expand ________________ and release sound waves Earth is struck ____________ times every second Grounding _________________ effects from charge build up If there is a ______________ to earth – relieves build up Grounded – it will transfer any ________________ charge to earth (big neutral object) Electroscope Chapter 8 Section 2 Electricity and Magnetism Basics of Magnets Magnetic ______________: exerts a force other magnetic objects Magnetic ______________: where magnetic force is strongest Field goes from North to _____________ Earth’s Magnetic Field Compass Compass needle is small _______________ – lines up with earth’s magnetic field From ___________________ magnetic pole to _________________ magnetic pole Electric Current and Magnetism _______________ electric currents create magnetic field in direction of current _________________ increases = increase ____________________ field Electromagnets Def: ____________________ magnet made by wrapping a ______________ coil carrying a current around an ___________ core Magnetic field in ______________ is stronger than ________________ wire _____________________: single wire wrapped in cylindrical coil Electromagnets _______________ _______________ Properties of Electromagnets Temporary b/c when _______________ stops – _________________ stops Increase strength – more ____________ in solenoid or more ______________ Useful b/c magnetic strength can be __________________ – used for work – motors and speakers Making Sound CD changing ______________ info changing ____________ current Electromagnet is ______________ or repelled by permanent magnet Moves speaker _____________ to make music Rotating Electromagnets ______________ current to change poles electromagnet ________________ Galvanometers Def: use electromagnet to measure ____________________ current Used in ______________ in cars Electric Motors Def: device that changes _________________ energy to ____________________ energy Simple Electric Motor 3 main parts: wire ____________, permanent ___________________ and battery Also have brushes – conducting _____________ connected to battery and a commutator – ___________ conducting metal ring Spinning Motor Commutator _______________ with coil as current runs through Step 1: Step 2: brushes ____________in contact with commutator Inertia keeps coil spinning Spinning Motor Step 3: commutator _____________ current – keeps spinning Step 4: commutator reverses current again - keeps spinning Chapter 8 Section 3 Producing Electric Current Mechanical to Electrical Energy Moving ________________ through magnetic field ______________ current Moving _______________ through wire loop electric current Electromagnetic induction: creating a current by _________________ magnetic field Generators Def: uses electromagnetic ________________ to transform mechanical energy to ____________________. Move a _____________ in a permanent magnet Switching Current Directions Each half-turn poles of coil _________________ current switches direction Coil keeps rotating current periodically changes ____________________ US generators rotate ____________ times/sec = 3,600 rotations/min Using Generators This type of generator is used in cars = ________________________ Lights, accessories, spark plugs Running _________________ turns coil Electricity to Your Home Huge generators in power plants rotate the permanent ____________________ and the coil stays still Electricity is generated in the ______________ A _______________________: (large wheel rotates when pushed by water, wind or steam) spins the ____________________ Some use thermal energy – heat water – turn turbine (_____________________ energy) – spin generator (electrical energy) Pg. 241 Direct and Alternating Currents Current in ________________ vs. electric generator Battery – ______________ Current (DC): flows in one direction through wire Wall Outlet – Alternating Current (AC): _____________________ direction of current in a regular pattern 60 cycles/s = 60 ________ changes direction ___________ times each second Transmitting Electrical Energy Electricity to your house Goes through ______________ lines – energy heat due to ____________________ in wires Reduce heat/resistance send at high voltage __________________ V BUT can’t use that high of voltage goes through __________________ Transformers Def: ___________________ or decreases the voltage of an alternating current. Has ________________ coil and secondary coil wrapped around same iron core Current goes in primary coil magnetizes core As AC current changes direction the _________________ of magnet change Changing poles creates electric current in _____________________ coil Types of Transformers __________________: increases voltage – outgoing is higher Primary coil smaller than secondary __________________: decreases voltage – outgoing is lower Primary coil is larger than secondary Transmitting AC Generator step-__________ tran. high voltage lines step-___________ tran. house