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Unit D – Electricity Static Electricity Static electricity: What does stationary mean? The charge is not flowing like a current. Ex. Lightning, static electricity on clothing, “shocking people” by touching them, shock from your car. Electrical Charge • Remember that opposites attract _______________________________________ • Most objects have an equal number of __________________________________________so they are considered _________________________________________ • When an object has more of one charge we say it is __________________________________ Ex. An object with extra electrons is negatively charged Draw the picture in your Notes! Positive Charge = Protons Negative Charge = Electrons Electrical Discharge Laws of Electrical Discharge: Charge Separation • Charged objects cause a charge separation when ______________________________________ For example, a negatively charged balloon, when brought close to a wall will cause the negative particles in the wall to be repelled, and therefore will be attracted to the positive particles left in the wall Record your Observations from the Balloon Activity Complete the Review Questions 1. What is the difference between a proton and an electron? 2. What does it mean to be “statically charged”? 3. How do like charges interact? 4. How do unlike charges interact? 5. A neutral object contains no charge. Is this true? Current Electricity • Is the charge on the eel a static charge or a current? Electrical Current Necessary Parts: 1. 2. 3. 4. Continuing the Flow • A conductor allows electricity to move through it easily • What are examples of conductors? • What is the opposite of a conductor? What are examples of these? Superconductors • Some metals are better conductors than others because they give ________________________ to the electrons that are flowing • Superconductors are perfect conductors- they have ____________________________________ • Extremely low temperatures help reduce the resistance in the superconductors • What’s the issue to running a superconductor at a low temperature? • Analyzing and Building Electrical Circuits Circuits • A circuit is a __________________________________________________________________ • Usually electricity moves through _____________________________but it can move through ____________________________________________________ Open Circuit Closed Circuit Series Circuit Parallel Circuit With a partner do the following lab– you have 20 minutes 1) Using any materials, make one light bulb light up 2) Using a battery, one bulb and 1 wire, make the light bulb light up 3) Using any materials, make 2 light bulbs light up 4) Make 2 light bulbs light up so that when you unhook one bulb, the other goes out 5) Make 2 light bulbs light up so that when you unhook one bulb, the other stays on What are some problems that may occur with this lab? Cells and Batteries • An electrochemical cell is a package of _____________________________________________ • One metal has _____________________________________________________than the other metal, so when a wire is attached to create a circuit the electrons get to move from one metal to the next, which creates a current • There are 2 ends on a battery, • Cathode = • Anode = There are 2 types of cells 1) –_____________________________________ the electrolyte is a paste • The electrolyte in a dry cell allows ions to flow which completes the circuit • An ion is an atom with a charge • ___________________________________ where electrons travel back to the cell • ___________________________________ where electrons travel from the cell • The 2 metals are called ______________________________________ • One electrode becomes positively charged, and the other becomes negatively charged. ALKALINE (having a basic electrolyte)- are some of the most common dry cells 2) ______________________________________ uses a liquid electrolyte • Wet cells often have a liquid such as _____________________________as their electrolyte • They are usually cheaper and easier to make than dry cells but are more dangerous • There are individual cells that alternate within the battery • Each cell has a positive and a negative plate • The terminals in the battery are at the top Think about it! • Is it correct to call a car battery a battery? Rechargeable Batteries • Primary cells: cells that can only be used one time • Rechargeable cells aka secondary cells- can be reused, the chemical reaction that occurred originally is forced to go back so it can be used again • Ni-Cd batteries are common secondary cells (made up of nickel and cadmium) Electrochemistry https://www.youtube.com/watch?v=8oeUE6dlP2A • Electrochemistry was begun which is the study of ______________________________________ • Scientists discovered that by putting more than one cell together they could increase the current and the power of the battery Electroplating Controlling the Flow of Electrical Current • _________________________________ have gas in them, when electricity is run through them they glow. • The circuit needs to be complete and needs to be controlled carefully Resistors • Resistance: • A resistor uses power (a load can be a resistor) • Resistance is measured in ohms –symbol Ω (omega) • The more resistance a substance has the more energy it takes from the electrons that pass through it Switches and Variable Resistors • Switches • A variable resistor or a rheostat can adjust the resistance in an object that the current flows through • Ex. Volume control on stereos, dimmer light switch Analyzing the Parts of a Circuit Draw the Components of the Shematic Diagram found Symbol Represents Description Conductor Conducts electricity through a circuit Cell Stores electricity (large bar is positive) Battery Combination of cells Lamp/ Light Bulb Converts energy to light Resistor Controls the amount of current in the circuit Switch Opens and closes circuit- allows current to flow Ammeter Measures the amount of current in a circuit Voltmeter Measures voltage across a device in a circuit Rheostat Variable resistor Motor Converts electricity to mechanical energy Fuse Melts if a current in a circuit is too high Tips for Drawing: • Conductors are always drawn in straight lines with 90 degree angles • The symbols are made the same size Conductor lines are not allowed to cross Complete the Practice Circuits. When you are finished all the drawings, try building the circuits 1. A closed circuit with a two-cell battery, a bulb and a switch. 2. An open circuit with a three-cell battery, a bulb and a switch. 3. A closed circuit with a three-cell battery, two bulbs, a switch and an voltmeter 4. A circuit with a two-cell battery and two bulbs that can are controlled by one switch. 5. A circuit with a three-cell battery and two bulbs, each of which are controlled independently by a switch. Draw the following: • A series including these things: Resistor, Switch, Voltmeter, Fuse, Battery made of 3 cells Draw a schematic diagram in parallel with the following: – 2 cells that power the whole circuit – A light turned on by one switch – A third switch that turns on or off all the lights together – 2 more lights turned on by a switch together As a class read about House Wiring and Microcircuits • What is a transistor? • What is a microcircuit? Electrical Safety https://www.youtube.com/watch?v=n6DXkVY8fzs https://www.youtube.com/watch?v=6Upae5eVXGg Electricity moves through the path of ____________________________– where it is the easiest to flow A _____________________________________ is a circuit where there isn’t any protection and the electricity moves quickly and can cause damage The _______________________________________ on a cord leads to the ground and is called a ground wire The number of amps of a current is more important in terms of the danger of being shocked Current from _______________________________________________will cause a painful shock and loss of muscles control What does this mean for a person being shocked? Different situations affect how bad an electrical shock is. One a dry day with running shoes on you may just feel a tingle from an electrical fence, but the same fence on a rainy day when you are barefoot could really hurt Safety Tips! Read the blue box on page 285 and choose three points to write down - • Fuse: – • Need to be replaced (like in a car) Breakers – Need to be cooled (like in your home) Lightening • A lightning strike can give a current up to ________________________________and it can kill • Lightning usually strikes at the highest point on a horizon. Lightning rods are connected to the ground through a wire to allow the discharge to dissipate to the ground
