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Transcript
ELECTRICITY ELECTRIC CHARGES Atoms are composed of _________ main parts. _______________, p+, positive, located in the nucleus; ________________, no, neutral, located in the nucleus; ____________________, e- , negative, located outside the nucleus in the electron cloud. Everything is made of ________________. Protons and electrons have a property called _________________________. An atom has __________ numbers of positive and negative charges so they _________________ each other out. Electrons can __________ from one atom to another atom. This movement is called ____________________. STATIC ELECTRICITY Some atoms hold their charges more ____________. Latin word “stasis” which means ___________. Static electricity is the ______________________ building up of charge on an object. Protons _______ move. Only _______________ move. In static electricity, the charges ___________________________ – they do not _________. When you walk across a carpet, __________________ causes electrons to move from the carpet to your shoe. This is a build-up of static electricity. You ____________________ the electricity by touching a _________________________. LAW OF CONSERVATION OF CHARGE When an object becomes charged, the electric charge is _______________________________________ – it just ________________ from another object. Static electricity is an ______________________ in the amounts of positive and negative charges on the surface of an object. Another way to generate static electricity is with a ______________________ generator. American physicist Robert Jemison Van de Graaf invented the Van de Graaf generator in 1931. There are _____________ ways to charge on object: 1. Charging by ______________ - The charge is transferred because of rubbing two objects together. Example: shoes on a carpet 2. Charging by ______________ - Involves the charging of one object by another object _______________________ direct contact. Example: balloon and rice cereal/electroscope 3. Charging by ______________ - Involves the ________________________________ of a charged object to a neutral object. Example: Van de Graaf generator Objects do not hold a static charge ________________ – objects tend towards ____________________ – they want to be neutral. When electrons move toward this equilibrium – static discharge occurs. - __________________ – water (a polar molecule) vapor in the air pulls electrons off negatively charged objects, preventing static charges to build up. - _______________________________ - objects reaching static equilibrium CONDUCTORS Allow the _______________________ of electricity; loosely bound electrons that are free to move from atom to atom. Examples: INSULATORS Insulators – ___________________ the flow of electrons; hold more tightly to their valence electrons. Examples: ELECTRIC CURRENT Define: REMEMBER: Conductors let electrons move ____________. Insulators do ________ let electrons move easily. A _________________________ has conductivity somewhere between an insulator and a conductor. Devices made of semi-conductors, notably _____________________, are essential components of most electronic circuits. There are __________ parts to an electric charge 1. ___________________ - For electrons to flow there must be a ___________________________ between two places. This is called voltage which is the ___________ that causes electrons to flow. It is ____________________________. Charges flow from ________ voltage to _______ voltage. Units: ________________________ 2. ___________________ - The measure of _________________________ per second are flowing through the wire is the amperage. Units: _________________. The number of electrons flowing per _________________. Electrical current is like the amount or __________________ _______________ flowing through the hose. There are two types of current: AC – __________ current and DC – ____________ current. 3. ____________________ - The tendency for a material to ______________ the flow of electrons. ___________________ materials have ___________________ amounts of resistance to the flow of electrons. Units: __________________. Examples: ___________, ____________, and _____________ have low resistance, which means that current can flow _____________ through these materials. __________, _____________, and __________ have very __________ resistance, which means that current ______________ pass through these materials easily. _________ wires provide more resistance than do _________ wires. Resistance in wires produces a _________ of energy (usually in the form of __________), so materials with no resistance produce no energy loss when currents pass through them. Resistance also depends on ______________________, usually increasing as the temperature ___________________. OHM’S LAW In a material, the current (I) is ________________ proportional to the voltage (V) and ____________ proportional to the resistance. Water in a Hose DC in a Wire Voltage (potential) (V) Electrical Units Current (I) Resistance (R) PRACTICE What is the current produced with a 9-volt battery through a resistance of 100 ohms? BATTERIES TWO TYPES: 1. ___________ Cell – the electrolyte is not really dry; but is a paste. – Standard AA, C, D type batteries, electrolyte is a paste. The “+” terminal is carbon. 2. ___________ Cell – the electrolyte is a liquid (car battery) – In a car battery, the electrolyte is sulfuric acid. Batteries have three parts: a _____________ (+), an _____________ (-), and an __________________. The cathode (________________) and anode (________________) at either end of a traditional battery are hooked up to an electrical circuit. The chemical reactions in the battery causes a ________________ of electrons at the anode. This results in an electrical ___________________ between the anode and the cathode - an ___________________ build-up of the electrons. The electrons wants to ______________ themselves to get rid of this difference. They do this in a certain way. Electrons _____________ each other and try to go to a place with ___________________ electrons. ELECTRICAL CIRCUIT Define: Four Parts: 1. Energy Source, 2. Load, 3. Wires, 4. Switch OPEN CIRCUITS – pathway is ___________. CLOSED CIRCUITS – pathway is ________________. SERIES CIRCUIT Provides only _________ path for the electrons to follow. A break in the circuit _________ the flow of electricity to all other parts of the circuit. With multiple light bulbs (more resistance) the current ______________ and the lights become ________________. Ammeters should be wired in series. RULES: 1. The _____________ current flows through each part of a series circuit. 2. The _________ resistance of a series circuit is equal to the ___________ of individual resistances. PARALLEL CIRCUIT The different parts of the circuit are on _______________ branches. A break (like a burned out light bulb) in the circuit ___________ stop the flow to the remaining devices. Multiple light bulbs will remain the __________ brightness since the resistance is ________ decreasing as it does in a series circuit. Each pathway can be separately ____________________ without affecting the others. Household circuits – Wired in ________________, with a standard of 120 volts. Voltmeters are wired in parallel. The ____________ paths, the _____________ the resistance. Water example again: added pipes coming from a large tank will allow ___________ water to flow out that a single pipe. Therefore as resistance _________________, current __________________; they are inversely proportional. RULES: 1. Voltage is the __________ across each component of the parallel circuit. 2. The _________ of the currents through each path is equal to the ____________ current that flows from the source. Question: What is the major difference between a series circuit and a parallel circuit – in your own words: SCHEMATIC DIAGRAMS All circuit drawings need at least the following: __________________, ______________________, __________________, ___________________, other items include connectors, meters, etc. There is a set of standard symbols used to represent these items in a diagram of the circuit. LIGHT BULB - Electricity flows through the circuit. If the bulb is _______________, so is the circuit. TRANSPORTING ELECTRICITY - A _____________________ is a device that increases of decreases alternating current generated by a power plant so it can enter homes safely. ELECTRICAL POWER - The ______________ at which electrical energy is transferred by an electric circuit. Use Joule’s Law: Power = ________________ x ________________. Unit: ____________. A ___________________________ is what the power company uses to determine how much electricity or energy you used. Energy used = ______________ (kW) x __________ (hours) or E= P x t. To find cost, you would multiply the _______________ by the ________________ per kilowatt hour. PRACTICE 1. 105 V are used to power an appliance that needs 15.0 amps. What is the power used? Power = current x voltage. 2. How much energy is used when this appliance is used for 30.0 days, 24hrs a day? Energy = Power x time. 3. If the power company charges 8¢/Kw-h, what is the cost of the energy above? Cost = Energy x price per kW hr.