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Friction Contact Induction Current Electricity What is the difference between static electricity and current electricity? Static electricity is stationary or collects on the surface of an object, whereas current electricity is flowing very rapidly through a conductor. The flow of electricity in current electricity has electrical pressure or voltage. Electric charges flow from an area of high voltage to an area of low voltage. Water pressure and voltage behave in similar ways. CURRENT • The flow of charges in a circuit is called current. Current (I) is measured in Amperes or Amps (A). Electricity - electrons moving through a metal wire. Direct current versus alternating current AC vs DC: What’s the difference? D.C. Electricity Direct Current A.C. Alternating Current Direct Current (DC) • Current flows in ONE direction • Think of water flowing in a stream • EX. Batteries Alternating Current (AC) • Current flows back and forth a regular intervals called cycles • EX. Comes from generators and is carried to your homes through power lines Measured using an ammeter, unit of electric current is ampere, A (amps) Voltage (Potential Difference) • Potential Energy – the energy stored in an object • Ex. Apple falling off a tree (converting potential energy into motion) – The greater the height of the apple, the greater its potential difference • Potential difference (voltage, V) is what causes a current to flow in a closed circuit • Measured using a voltmeter Electrochemical Cells • Ex. BATTERIES!!! – a combination of electrochemical cells • A package of chemicals that converts chemical energy to electrical energy that is stored in charged particles. • A simple electrochemical cells includes: – Electrolyte: a liquid/paste that conducts electricity (ex. Citric acid) – Electrodes: 2 metal strips that react with the electrolyte (one will gain e-(-ve), one will lose e(+ve) (ex. zinc, copper) 2 Types of Electrochemical Cells Wet Cell • Uses a liquid electrolyte • Contains two connected plates made of different metals or metal compounds in a conducting solution. • Most car batteries have a series of six cells, each containing lead and lead oxide in a sulfuric acid solution. 2 Types of Electrochemical Cells Dry Cell • Uses paste instead of a liquid electrolyte • The zinc container of the dry cell contains a moist chemical paste surrounding a carbon rod suspended in the middle. Term CURRENT VOLTAGE Symbol I Definition - the flow of electrons through a conductor Amperes (A) - also known as “Potential Difference” “push/force” of electricity Potential energy per quantity of electrons Volts (V) V - RESISTANCE R Measured in (Units) measures how easily electricity flows along a certain path ohm What is electrical resistance? Resistance (R)is the opposition to the flow of an electric current, causing the electrical energy to be converted to thermal energy or light. The metal which makes up a light bulb filament or stovetop eye has a high electrical resistance. This causes light and heat to be given off. The unit for measuring resistance is the ohm (Ω). What are electric circuits? • Circuits typically contain a voltage source, a wire conductor, and one or more devices which use the electrical energy. Drawing Circuit Diagrams Electrical Circuit Symbols Symbol Component CELL, BATTERY Function - Electrical source Longer side is the positive side The shorter side is the negative side - SWITCH - Opens and closes the circuit - VOLTAGE - Measures voltage through a device - AMMETER - Measures current through a device - MOTOR - A type of resistor - (LAMP) LIGHT - - RESISTOR - Specific load Converts electricity to heat and light General load Converts electricity to heat - CONDUCTING WIRE - Conductor Allows electrons to flow Drawing Circuit Diagrams RULES 1. Always use a ruler to draw straight lines for the conducting wires 2. Make right-angle corners (∟) so that your finished diagrams is a rectangle • Contain 4 basic parts: – Electrical source – Switch – Load – Conducting wire What is a series circuit? • provides a single pathway for the current to flow. • If the circuit breaks, all devices using the circuit will fail. What is a parallel circuit? • has multiple pathways for the current to flow. • If the circuit is broken the current may pass through other pathways and other devices will continue to work. Switch 1 Switch 2 Lamp 1 Lamp 2 What is the difference between an open circuit and a closed circuit? A closed circuit is one in which the pathway of the electrical current is complete and unbroken. An open circuit is one in which the pathway of the electrical current is broken. A switch is a device in the circuit in which the circuit can be closed (turned on) or open (turned off). How is household wiring arranged? Most household wiring is logically designed with a combination of parallel circuits. Electrical energy enters the home usually at a breaker box or fuse box and distributes the electricity through multiple circuits. A breaker box or fuse box is a safety feature which will open. References • A Dercho • Investigating Science 9 -Pearson