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“What is Electricity?” Review Atomic Structure • What is an Element? Elements The simplest form of matter • What is an Atom? Atoms The smallest piece of an element that contains all properties of that element • What 3 particles make up atoms? Components of an Atom Electrons Negatively charged atomic particles Protons Positively charged atomic particles Neutrons Uncharged atomic particles • What determines the atomic number of an atom? • What is the atomic number of Copper (Cu)? Atomic Number The atomic number is equal to the number of protons in the nucleus of an atom. The atomic number identifies the element. How many protons are in this nucleus? Periodic Table of Elements NASA Which element has 4 protons? Electrons For this unit, we mainly care about electrons in atoms. Why? It is important to understand the “how and why” of the movement of electrons to understand electricity. • Draw a representation of a Sulfur atom (Atomic Number 16). • Draw a representation of a Helium atom (Atomic Number 2) Filling order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, … Electron Orbits Atoms like to have their valence level either filled (8) or empty(0) of electrons. How many electrons are in the valence level? 6 Sulfur has space to gain two electrons in its valence level. • What is a valence electron? • How many valence electrons do conductors have? • How many valence electrons do insulators have? • How about semiconductors? Conductors and Insulators Conductors Insulators Electrons flow easily between atoms Electron flow is difficult between atoms 1-3 valence electrons in outer orbit 5-8 valence electrons in outer orbit Low Electronegativity High Electronegativity Good Conductors: Silver, Copper, Gold, Aluminum . . . Examples: Mica, Glass, Rubber, Plastic . . . What is a Multimeter? An instrument for measuring the properties of an electrical circuit Manual vs. Auto Ranging Where should you set the meter if you expect a reading around . . . 6 volts 50 millivolts 800 millivolts 800 volts 125 volts History Ben Franklin suggested that . . . + . . .opposite charges attract and like charges repel. - History Ben Franklin suggested that . . . . . .opposite charges attract and like charges repel. The Law of Charges explains why the electrons continue to be bonded to the nucleus. + + Electron Flow An electron from one atom can knock out an electron from another atom. Electron Flow Electricity is created as electrons collide and transfer from atom to atom. Play Animation What Makes Up Electricity? Let’s compare it to something we know --- Water! Water Analogy Tank Faucet Pipe Tank = Battery Pipe = Wiring Faucet = Switch • What is current? Current Current: The flow of electric charge Tank (Battery) Faucet (Switch) Pipe (Wiring) When the faucet (switch) is off, is there any flow (current)? NO When the faucet (switch) is on, is there any flow (current)? YES Current in a Circuit off on When the switch is off, there is no current. When the switch is on, there is current. • What is voltage? Voltage Voltage: The force (pressure) behind the flow of current Tank (Battery) Faucet (Switch) Pipe (Wiring) When the faucet (switch) is off, is there any pressure (voltage)? YES – Pressure (voltage) is pushing against the pipe, tank, and the faucet. When the faucet (switch) is on, is there any pressure (voltage)? YES – Pressure (voltage) pushes flow (current) through the system. Voltage in a Circuit off on The battery provides voltage that will push current through the bulb when the switch is on. • What is resistance? Resistance Resistance: The opposition to the flow of current. Tank (Battery) Faucet (Switch) Pipe (Wiring) What happens to the flow (current) if a rock gets lodged in the pipe? Flow (current) decreases. Resistance in a Circuit off on Resistors are components that limit the flow of electricity. Reducing current causes the bulb to become more dim. What types of electricity are there? Types of Electricity Static Electricity The electrical charge an object develops as a result of having an unequal number of protons and electrons. Current Electricity The movement of electrons through a conductor. Static Electricity • Uncontrollable Electricity • Lightening • Static Cling • Wool socks on a carpet “shocks” • What are the two types of current electricity? • What is the difference between these two? Current Electricity Two Types: Direct Current (DC) Alternating Current (AC) Direct Current The electrons flow in the same direction all the time, from negative to positive. - + Direct Current Comes from • Batteries • Converted from Alternating Current Used for electronic devices including • Computers • iPods • Cell phones • Anything that has a “charger” Alternating Current The electrical current (movement of electrons) changes direction. Alternating Current Comes from Generators • Coal burning and nuclear power plants • Hydroelectric power plants • Wind and solar generators Used for • Motors • Heaters • Lights • Anything that plugs into the wall What is a Magnet? An object that is surrounded by a magnetic field and has the property of attracting iron or steel Where are Magnets? Magnets. . . Generate electricity Image courtesy of DOE/NREL Are in motors Image courtesy of DOE/NREL Where are Magnets? Magnets. . . Power car windows & locks Are used in Magnetic Resonance Imaging (MRI) Image courtesy of NASA • If a large magnet breaks into the small pieces what will their poles be? North and South Poles of a Magnet Magnets have a north and south pole. • If a magnet is broken into smaller pieces, each piece will still have a north and south pole. • Opposite poles attract, like poles repel. N N S N N S S S S N • How do compasses work? The Earth as a Magnet The Earth is a large magnet. Compasses work as a result of the Earth’s magnetic field. • What is an electromagnet? Electromagnets Magnets are created by passing a current through a wire. Electromagnets are generally wire wrapped around an iron core. Electromagnets are turned on and off when the current is switched on and off. • How can you switch the poles of an electromagnet? Electromagnets N S Electromagnet ends change between north and south depending on the direction of the current. S N • What parts make up a motor? Parts of a Basic DC Motor Motor: A device used to convert electric energy into mechanical energy. Brush DC Source Commutator N N Permanent Magnet Armature S Permanent Magnet S Commutator Brush Parts of a Small DC Motor Brushes Wire Connections Permanent Magnets Armature Commutator • What is an electric generator? Electric Generators Generator: A device used to convert mechanical energy into electrical energy. Mechanical motion turns the armature which creates current. Many DC motors can function as a generator. N N S S • Explain the steps by which electricity goes from the power plant to your home. From the Power Plant to Your Home Image courtesy of Sacramento Municipal Utility District Power plants generate electricity. From the Power Plant to Your Home Step up transformers increase voltage for transmission across large towers. Increased voltage increases efficiency. From the Power Plant to Your Home Images courtesy of DOE / NREL Large towers transmit electricity over long distances. From the Power Plant to Your Home Step down transformers reduce voltage at substations to acceptable levels for the end user. From the Power Plant to Your Home Electricity arrives at your home at a junction box. Usage is measured with a meter. • Briefly explain how Maglev Trains work