CH 20 .1

Electric Charge and Static Electricity

True False Statement True False

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

electronsSI Unit

Coulomb (C) 6.24 x 1018 electrons

Electric Forces

Like charges 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

CH 20 .2

Electric Current and Ohm’s Law

True False Statement True False

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

Electric Conductor Electric Insulator

Material electric charge can flow easily through

Cu, Ag

Material electric charge cannot flow easily through

Wood, plastic, rubber, air

Conductors and Insulators

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

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

Voltage

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

CH 20 .3

Electric Circuits

True False Statement True False

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 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 EnergySI 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

Home Safety Personal Safety

Fuse Prevents current

overload Blowing a fuse-

melting a fuseCircuit Breaker

Switch the opens when a current in a circuit is too high

Grounding Transfer of excess

charge through a conductor to Earth

Electrical Safety

CH 20 .4

Electronic Devices

True False Statement True False

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 The science of using electronic current to

process/transmit informationElectronic Signal

Information sent as patterns in the controlled flow of electrons through a circuit

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

Electronic Signals

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