 All matter is made up of atoms  atoms are made up of protons, electrons and neutrons  Protons and electrons can transmit energy in the form of electricity  When 2 different materials are brought into close contract some electrons move to the other material  Causes the material to become electrically charged (positive charge or negative charge)

 Negatively charged-more electrons, less protons  Positively charged-more protons, less electrons  Static electricity is produced from the buildup of positive and negative charges  Principles of Electricity:  Opposite charges attract  Like charges repel

 When a charged balloon is brought near a wall, its extra negative charges repel the negative charges on the wall  The negative charges move to the other side of the wall  The wall becomes positively charged  The balloon has a negative charge causing it to be attracted to the wall and stick

 Conductors:  Electrons move through a material easily  Can cause a spark  Ex: human tissue touching metal doorknob  Insulators:  Electrons do not flow easily through a material  Ex: human tissue touching plaster will not cause an electric spark

 It is dangerous to touch a bare wires  Grounding wires of an appliance connects the metal case to the ground through the household wiring  If a dangerous charge builds up the grounding wire enables the appliance to share the change with the ground  Grounding wires protect us from getting dangerous shocks

 Produced by static electricity  Negative charges build up in a cloud  The ground has a positive charge  When enough negative charges build up they form a path to the ground  Surge of electric energy heats the air to glow-we see lightning  Heat makes the air expand rapidly-we hear thunder  Lightning has high electric energy, which is deadly

 A path along which charged particles can travel  Electrons move through the wires and bulbs  Consist of a source of electricity, devices and connecting wires  The source of electricity starts pulling and pushing on the electrons and the electrons start flowing to the positive end of the source  A flow of charged particles moving through a circuit is called a current  Electrons move from negative to positive

 Sources of electricity are rated by voltage  As the voltage becomes greater, more negative and positive charges can build up at one end  Resistor-opposes a flow of electrons  It makes the current smaller by opposing the flow of electrons  The lamp could blow out without the resistor  The resistor reduces the current of electrons flowing through the lamp to a safe level

 Short circuit could occur if the current is not reduced  If the current is not reduced, electrons will collide causing the wires to heat up  This heat could cause a fire

 Only one path for the electric current  Their voltages are added together  Increased crowding of electrons at the negative end of one battery  Increased removal of electrons at the positive end of the other battery  Puts more force on electrons in the wires and bulbs, which produces more current  Light bulbs act as a resistor to prevent a short circuit from occurring  The flow of charges is the same at any point

 More than one path for current  Electricity source makes each path feel the same overcrowding of electrons  Total current increases when another path is added, even though another resistor is present  Current in each path depends on the strength of its resistor  Currents are added together to find the total current  Total current is the same at any point

 Incomplete circuit  Switch is in the off position  There is no current  Electrical devices do not receive electric energy  Copy circuit 1 in Notebook

 Complete path for a current  Current flows in the wires and devices  Current transfers energy to the device  Switch is in the on position or closed  Copy Circuit 2 in Notebook

 Attract metal objects made of iron, cobalt or nickel  Attract and repel other magnets  Have 2 poles: north-seeking pole and a south- seeking pole  South pole of one magnet repels the south pole of another  A north magnetic pole attracts a south magnetic pole  The attraction is strongest at the poles

 Magnetism comes from the motions of electrons in atoms  Moving electrons cause atoms to line up in the same direction  Permanent magnets-atoms always stay lined up  If brought near and object that is nonmetallic, there is no attraction

 Devices that are made magnetic by an electric current  Magnetism results from moving electrons in a current-carrying wire  If brought near a nonmetallic object, there is no attraction

 Is the area around a magnet in which other magnets can feel attraction or repulsion  Magnetic force moves from the north pole to the south pole and form closed loops  Attraction or repulsion is strongest where the arrows are most crowded

 Tilt of Earth’s axis causes the magnetic poles to be off true geographic north and south poles  Magnetic field is not evenly shaped  Compass needle always points to the magnetic north pole  Earth’s magnetism is likely caused by electrical currents in a fluid metal layer around Earth’s inner core

 Used to power toys, elevators, fans, air compressors, cranes, some cars and bicycles  The spinning force comes from an electromagnet  A loop of wire is placed between 2 permanent magnets  When current passes through the wire, the loop becomes an electromagnet

 Magnetic resonance imaging (MRI)  Strong magnetic field produced by electromagnets cause the nuclei in the patients body to behave like magnets and line up with the magnetic field  This enables radio waves to produce images of tissues inside the body

 Speakers depend on electromagnets to operate  Cone in a speaker has an electromagnet  Current passes through the electromagnet causing the cone to vibrate and produce sound

 A device that produces a current in a solution  Use chemical reactions to produce an electric current  Charged particles always move in the same direction-direct current  Consists of 2 different metal plates in a solution  Produces a voltage-the difference in the amount of potential energy between the plate  Voltage is measured in volts

 The amount if current can be measured by an ammeter and the unit is ampere or amp

 Produce an electric current using a moist conducting paste  Chemical reactions between the paste and the plates produce a current  Ex: battery

 Uses mechanical energy to make electricity  It produces an alternating current  Electric power plants use generators to produce electricity for homes and businesses  Transformers are used to increase or decrease the voltage of the current

 Electric current produced by huge generators  Power lines connect the power plants to homes in cities and towns  Electric current from a generator first passes through a transformer that increases the voltage anywhere from 120,000 to 500,00 volts  Before the current comes into our homes it passes through another transformer that decreases the voltage

 Household circuits use 120 volts  The total current for an entire house is 100 or 200 amps  You can run two appliances on the same circuit, which has 20 amps, as long as they do not use more amps combined  Short circuits occur when too much current flows through a wire  Fuses and circuit breakers protect homes from catching on fire

 Any form of energy can be changed into other forms  Electrical energy can be changed into 4 other types of energy 1. Mechanical Energy  Electric energy changes into mechanical when any device that uses a motor is used  Examples: food blenders, electric fans, power tools

2. Heat  Coils get very hot because of an electric current  Electrons from the current collide with the atoms in the coils  Temperature of the coils rise  Ex: heaters, electric blankets, toasters, hair dryer 3. Sound  Current causes electromagnets to move a diaphragm back & forth producing sound waves  Ex: speakers

4. Light  2 types of light bulbs 1. Incandescent  Contain a thin metal wire or filament that acts like a resistor  Electric current heats it causing the filament to give off heat and visible light  Only 12% of the energy is light  Rest of energy is wasted as heat

2. Fluorescent  Produce more light than heat  Series of collisions causes gas inside the glass to produce light  Fluorescent coating on the outside glows