Electricity Chapter 20 Electricity Concept Symbol Unit Current

Electricity Chapter 20

Electricity Concept Symbol Unit Current I Ampere (A) Resistance R Ohms (Ω) Voltage V Volts (V) Power P Watts (W) end

Electric Charge • Remember: • Electrons have a Negative Charge • And they Move Around! • Gaining Electrons makes atoms Negative • Losing Electrons makes atoms Positive • Opposites Attract and Likes Repel end

Electric Charge • Charged objects create an Electric Field – Area where the charge affects other charged particles – This field creates a force on other objects • Attraction or Repulsion end

Electric Charge • To give an object a charge, use Static Electricity – Charge builds-up, but does not flow – Rubbing your socks on the carpet – It will discharge, when a conductor touches the object and allows electricity to flow • Touching a door-knob – 3 ways to charge an object: end

Electric Charge • Friction – Rubbing 2 objects together – Electrons move to 1 of the objects – Rubbing socks on the carpet or balloon on your hair + - +- - + + Charge = 0 + + - + + Charge = 0 end Rub Together + +- + + Charge = +2 - ++ - -+ Charge = -2

Electric Charge • Conduction – A charged object touches an uncharged object – The charge spreads out over both objects + - +- - + + Charge = 0 + - - + Charge = -4 Touch Together + - +- - +Charge = -2 end + - - + + + Charge = -2

Electric Charge • Induction – A charged object comes CLOSE, but DOES NOT TOUCH an uncharged object – Electrons in the uncharged object move around • One side becomes positive and the other negative • It becomes POLAR!!! + - +- - + + Charge = 0 Positive Side Negative Side + - - + - Charge = -4 end - + + Charge = 0 + - - + Charge = -4

Bellringer: 12/15/15 1. Electricity is the flow of _____. 2. What are three ways objects can become charged? 3. STOTD

Electric Charge • Insulators • Materials that do not allow electrons to flow • Plastic, Styrofoam, Rubber • Conductors • Materials that allow electrons to flow • Metals end

Ohm's Law • Current (I) – The flow of electrons • More Current = More Electrons Moving • Measured in Amperes (A) aka “amps” – 2 types: • Direct Current (DC)- Used in batteries • Alternating Current (AC)- Used in homes end

Ohm's Law • Resistance (R) – Slows Down or Stops electrons from moving – Measured in Ohms (Ω) – Insulators (Rubber) have a high resistance – A superconductor has no resistance end

Ohm's Law Factors High Resistance Low Resistance Length of Wire Long Short Thickness of Wire Thin Thick Temperature Cold Hot end

Ohm's Law • Voltage (V) – The energy available to move electrons • The push of electrons through a wire • Measured in volts (V) – Also known as the Potential Difference end

Ohm's Law • Ohm's Law end

Bellringer: 12/8/14 1. What is the current produced by a voltage of 120 V through a resistance of 0. 5 Ω? 2. What resistance would produce a current of 120 A from a 12 V battery? 3. What voltage is needed to produce a current of 200 A, through a resistance of 0. 005 Ω? 4. STOTD end

Ohm’s Law • Electrical Power (P) – The rate that electrical energy does work or is transformed into other forms of energy – measured in Watts (W) – Also measured in kilowatts (k. W) end

Ohm’s Law 1. A 12 volt battery produces a current of 0. 8 A. What is its power in a circuit? 2. A 60 W light bulb is operating on 1. 2 A. What is the voltage? 3. A 500 W oven is operating on a potential difference of 240 V. What is the current being used? end

• Electric Circuits – A complete path that electrons can travel – Circuit diagrams are used to represent different parts + side Battery Switch • Light/Power switch end Resistor • Something that uses electrical energy • Light bulb, computer, t. v. , … Open Closed • A break in the circuit • Circuit is complete • Power is OFF • Power is ON

Circuits R = 42 Ω • There are 3 types of circuits: – Simple, Series, Parallel • Simple Circuit – 1 battery and 1 resistor – 1 path for electrons to follow – Use Ohm’s Law to solve I = 0. 3 A V= ? end

Circuits R=? I = 13 A I=? V= 240 V end R = 4. 7 Ω V= 120 V

Circuits • Series Circuits – 1 battery and 2 or more resistors – 1 path for electrons to follow – If 1 resistor stops working, then everything stops working – Includes Simple Circuits – Current is the Same everywhere on the circuit – Old Christmas lights end

Circuits R 1 = 2 Ω R 1 = 0. 2 Ω I=7 A I=? R 2 = 4 Ω V=? R 2=4. 1 Ω V = 158 V Add the resistors together to get the Total Resistance. Then use Ohm’s Law to solve the circuit end

Circuits • Parallel Circuits – 1 battery and 2 or more resistors – Many paths for electrons to follow – If 1 resistor stops working, then the rest keep working – Voltage to each Branch is the Same – You house is wired in parallel end

Bellringer: 12/16/15 • Identify the circuits below and solve the equation using Ohm’s Law: R = 42 Ω 1. 2. R = 2 Ω 1 R 2 = 4 Ω I = 0. 3 A I=7 A V= ? 3. STOTD V=?

Circuits R 3 Multiple branches R 2 R 1 end

Bellringer: 12/10/14 1. How are simple and series circuits different? 2. Draw an example of a simple circuit. 3. Draw an example of a series circuit. 4. STOTD

Bellringer: 12/11/14 1. How can you be safe working with electricity? 2. STOTD

Electrical Safety • Fuses – Thin wire that allows current to flow. – Too much current passes through, Wire melts and electricity is stopped • Must be replaced each time it is “Blown” • Circuit Breakers – 2 strips of different metals that are touching – Too much current = They expand separate • Electricity is stopped • Can be reset after the metal cools down end

Electrical Safety • Ground-Fault Circuit Interrupter (GFCI) – Measures current in and out of a resistor – If they are not equal, it shuts off – Used in bathrooms and kitchens • 3 -Prong Plug – Used on things with a metal exterior – If a short occurs, electricity goes through the 3 rd prong instead of your body! end

Electrical Safety Current Level 0. 001 A (1 m. A) 0. 005 A (5 m. A) 0. 006 – 0. 030 A (6 -30 m. A) 0. 050 – 0. 150 A (50 -150 m. A) 1 – 4. 3 A (1000 -4300 m. A) 10 A end (10000 m. A) Effect Slight tingling sensation Slight shock Painful shock, loss of muscular control Extreme pain, severe muscular contractions, breathing stops, death is possible Nerve damage, heart stops, death is likely Severe burns, heart stops, death is probable

Ohm's Law Volts Current 250 Resistance 10 50 300 5 100 35 end 50

Circuits Series Parallel Add More Batteries Voltage is Increased Add More Resistors n. You Voltage remains the same Less current will go to each resistor will decrease the voltage n. Provides less power to each resistor end

Magnetism Chapter 21

Magnets • Magnetism • Force of attraction or repulsion between two objects. • 2 sides to every magnet: • North (N) • Points to magnetic north • South (S) • Points to magnetic south end

Magnets • Magnetic Forces – Opposites Attract and Likes Repel!!! – Closer to the Pole = Stronger Force – The area that the magnetic force acts on objects is called the Magnetic Field end

Magnets ► We draw Field Lines to show the area affected by the Magnetic Field The arrow goes from North to South More Lines = Stronger Field end

Magnets • When 2 magnets come close together the Field Lines interact with each other – Remember they go from N to S Attraction end

Magnets Repulsion end

Magnets • Magnetic Domain • Area where most atoms have the same magnetic charge. • Point in the same direction • Something can be made into a magnet through Magnetic Induction • Force all Magnetic Domains to point in the same direction end

Magnets • When you create a magnet, it can either be temporary or permanent • Temporary • Easily magnetized but loses strength quickly. • Permanent • Hard to magnetize but keeps its strength a long time. • Common Magnetic Elements • cobalt, nickel, iron, aluminum end

Bellringer: 12/17/15 • You have 15 minutes to start working on Ch 21 vocabulary. We will start notes at 11: 00 am • Write your STOTD in your notebook.

Electromagnets ► As electricity runs through a coiled wire, it creates a magnetic field The Magnetic Field lines look the same as a bar magnet Known as an Electromagnet This property allows us to use electricity to create magnets of any strength And to make things magnetic end

Electromagnets • Electromagnets have 3 parts: 1. Power Source • Need to be able to change the Current in the circuit 2. Wire 3. The Core end Wire wrapped around the core Core

Electromagnets ► To increase the strength of an electromagnet: Increase the current Increasing the number of turns in the wire ►Wrap the wire more times around the core Use a core that is easily magnetized end

Motor vs. Generators Motor • Oerstead • Electrical Energy into Mechanical Energy Generator • Faraday • Mechanical Energy into Electrical Energy • Electromagnets • Electromagnetic Induction end

Transformers • Changes the amount of Voltage in AC circuits • 2 Types: • Step Up • Increases voltage • Step Down • Decreases voltage end