ch 20.1 electric charge and static electricity. truefalsestatementtruefalse like charges attract,...
TRANSCRIPT
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
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
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
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
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