# Electric Charge and Static Electricity

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Electric Charge and Static Electricity

Like charges attract, opposite charges repel
True False Statement Like charges attract, opposite charges repel Electric charge is due to an excess or shortage of electrons Law of Conservation of Charge says that charge is constant You can charge an object by touching, friction and induction The SI unit for static electricity is the coulomb

Electric Charge Property that causes subatomic particles (_____, ______) to attract/repel each other 2 Types Positive- Protons Negative- Electrons Net Electric Charge Excess or shortage of electrons SI Unit Coulomb (C) 6.24 x 1018 electrons

Electric Forces Like charges Opposite charges Electric Force
Repel Opposite charges Attract Electric Force Forces of attraction and repulsion between electrically charged objects Charles Coulomb Discovered electric forces are similar to the law of Gravitation

Electric Fields The strength of an electric field depends on
The amount of charge that produces the field The distance from the charge The force depends on The net charge in the object The strength and direction of the fields position

Static Electricity and Charging
The study of the behavior of electric charges and how charge is transferred Law of Conservation of Charge Total charge in an isolated system is constant 1. Charging by Friction Ex. Rubbing a Balloon in your hair Electrons move due to attraction

Static Electricity and Charging
2. Charging by Contact Ex. Van de Graaff generator 3. Charging by Induction Ex. Reaching for a doorknob after rubbing feet across carpet Induction- transfer of charge without contact between materials

Static Discharge Occurs when a pathway through which charges can move forms suddenly

Electric Current and Ohm’s Law
Ch 20.2

DC current is current in all direction, while AC current reverses
True False Statement DC current is current in all direction, while AC current reverses Thickness, length and temperature affect resistance Ohm’s Law says resistance(R), voltage(V) and current(I) are co-related Potential difference is also voltage, or the difference between 2 places in an electric field Conductors help current to flow easily while insulators prevent current from flowing

Electric Current Continuous path through which charge can flow SI Unit
Ampere/Amp (A) 1 C/s 2 Types of Current 1. Direct Current (DC) Charge flows in 1 direction Flashlights, battery operated machines 2. Alternating Current (AC) Charge flow reverses direction Electricity in buildings

Conductors and Insulators
Electric Conductor Electric Insulator Material electric charge can flow easily through Cu, Ag Material electric charge cannot flow easily through Wood, plastic, rubber, air

Resistance Opposition to the flow of charges in a material SI Unit
Ohm Superconductor Material that has almost zero resistance when it is cooled to a low temperature 3 Factors Affecting Resistance Thickness Length Temperature

Voltage In order for a charge to flow in a conducting wire, the wire must be connected in a complete loop that includes a source of electric energy

Voltage Battery Solar cells, generators
Potential Difference Voltage Sources Charges flow from higher to lower potential energy PD- difference in electrical PE between 2 places in an electric field SI Unit J/C or Volts Also called voltage Battery Device that converts chemical energy to electrical energy Solar cells, generators

Ohm’s Law Voltage(V) in a circuit equals the product of the current(I) and the resistance(R) Increasing the voltage increases current Keeping the same voltage and increasing resistance decreases the current V = I x R Ex. 3 amps x 3 ohms= 9volts

Electric Circuits Ch 20.3

Circuit diagrams use symbols to represent an electrical circuit
True False Statement Circuit diagrams use symbols to represent an electrical circuit A closed circuit stops, while an open circuit is free to flow Series circuits only have one way to flow Parallel circuits have 2 or more paths in which to flow A fuse prevents current overload, and melts in over use

Circuit Diagrams Electric Circuit Circuit Diagrams Open Circuit
Complete path through which charge can flow Circuit Diagrams Use symbols to represent parts of a circuit, electrical energy and devices run by electrical energy Open Circuit Open switch = current stops Closed Circuit Closed switch = complete flow of current

Series Circuit Charge has only 1 path through which it can flow
If 1 element stops working, none of the elements can operate

Parallel Circuit Electric circuit with 2 or more paths through which charges can flow If 1 element stops functioning the rest can still operate

Power and Energy Calculations
Electrical Power Rate at which electrical energy is converted to another form of energy SI Unit J/s or Watt (W) Kilowatt (kW) P(watts)= I(amps) x V(volts) Electrical Energy SI Unit W s kW hr E= P x t

Math Practice pg 611 1. 3. 2.

Electrical Safety Electrical Energy Safety Correct wiring Fuses
Circuit Breakers Insulation Grounded Plugs

Electrical Safety Fuse Circuit Breaker Grounding Home Safety
Personal Safety Fuse Prevents current overload Blowing a fuse- melting a fuse Circuit Breaker Switch the opens when a current in a circuit is too high Grounding Transfer of excess charge through a conductor to Earth

Electronic Devices Ch 20.4

Analog signals change voltage, while digital signals change current.
True False Statement Analog signals change voltage, while digital signals change current. Vacuums are the best way to control electronic signals, compared to solid state components A diode has a n-type and p-type semiconductor A n-type semiconductor flows protons, while a p-type semiconductor flows electrons An integrated circuit replaces many vacuums and is also called a microchip

Electronic Signals Electronics Electronic Signal
The science of using electronic current to process/transmit information Electronic Signal Information sent as patterns in the controlled flow of electrons through a circuit

Electronic Signals Analog Signal Digital Signals Smoothly varying signal produced by continually changing the voltage or current AM radio Encodes information as a string of 1s and 0s DVDs

Vacuum Tubes Change alternating current into direct current
Increase the strength of a signal Turn a current on or off Cathode Ray Tube Used in computer monitors, TVs Phosphors glow red, green or blue

Semiconductors Crystalline solid that conducts current only under certain conditions N Type Semiconductor Current is a flow of electrons Made by adding P to Si P Type Semiconductor Appears as though positive charge flows Made by adding B to Si

Solid State Components
Used solids instead of vacuums to control current 1. Diodes Solid state component that combines N Type and P Type semiconductors Flows from N to P Can change alternating current to direct

Solid State Components
2. Transistors Solid state component with 3 layers of semiconductors Used as a switch or amplifier 3. Integrated Circuits Thin slice of Si containing many solid state components Chips or microchips Perform as well as a network of vacuums

Communications Technology
Computer Programmable device that stores and processes information Communication devices use microchips to make them Portable Reliable affordable