Download Electricity

Electrical
Energy
State Correlation: 2d
Discuss
Imagine a world without
electricity
What is Electricity?
• Electricity is a form of energy produced
by the flow of electrons from one point
to another.
• Conductors are materials through which
electricity moves easily
– Most metals are good conductors
• Ex. Copper & Aluminum
• Most wires in homes are made from copper
• Insulators are substances that are poor
conductors and do not allow electrons to
flow through them
– Ex. Rubber, glass, plastic, air, & wood
Law of Electric Charges
Two types of charges: Positive & Negative
• Like charges repel
+ +
- • Unlike Charges attract
+-
Electric Currents
• Current electricity is a continuous
flow of electricity or the amount of
charge that moves past a certain
point each second
– SI unit for current is the ampere or
amp
Controlling a Current
• Voltage: in a battery it is the measure
of how much electrical potential energy
each electron can gain
– Standard Unit: Volts
• Resistance: the measure of how
difficult it is for electrons to flow
through a material – Standard unit:
Ohms
– Insulators have a higher resistance than
conductors
Affecting Resistance
• Length of a conductor
– The longer the wire the greater the resistance
– Analogy: Long hose verses a short hose – which one
will water flow from the fastest?
• Size/width of a conductor
– The thinner the wire the greater the resistance
– Analogy: thick hose verses a thin hose – which one
will water flow from the fastest?
• Real worlds example:
– long, thin coiled tungsten wires are used in light bulbs
because it has a high melting point
– Electric Companies have to use high voltage to send
electricity in the long wires from the power plant to
your house, but the a lower voltage is required for
electricity to flow throughout your house
Volts
Which circuit will be brighter? Explain
Review
• Which of the following has the
greatest resistance? Least
Resistance?
– Short, thick wire
– Long, thick wire
– Short, thin wire
– Long, thin wire
(least resistance)
(greatest resistance)
Currents Flow In Circuits
• An electric circuit is a complete
path for the flow of electricity
– Open circuits have a break in the
path
– Closed circuits have no breaks in the
path
Parts of a Circuit
• Energy Source: the object that pushes
electric charges through a closed
circuit
– Batteries have a positive and a negative
terminal. One terminal repels charges
while the other terminal attracts charges
providing the push that keeps the electric
charges moving
– The greater the voltage the greater the
push
• Load/device: the object that the
electrical energy is delivered to (light
bulb)
Parts of a Circuit
• Wires: connect the energy source to
the load
– Often made of copper and insulated with
plastics or rubber
• Switch: made to open and close a
circuit by bringing together or
separating two pieces of metal
Circuit Symbols
Types of Circuits
• Series Circuit: single path of electricity
through devices attached to the circuit
– If one device stops working the circuit path
of electricity is broken so no other devices
work
Types of Circuits
• Parallel Circuit: has two or more
devices/loads wired so that the electricity
flows through separate branching paths to
each device
– If one device stops working the other devices
continue to work through their own path of
electricity
Comparing & Contrasting
Circuits
Protecting Electric
Circuits
• In a circuit, the more devices, the
more current & the more amps the
more heat energy is produced
• Fuses/circuit breaker: a device that
protects a circuit from
overheating and causing a fire
– If the current becomes too large a
piece of metal melts or a switch
opens the circuit to stop the current
Energy Transformations
• Law of Conservation of Energy: states that
energy cannot be created nor destroyed, but
it can change from one form to another
• Chemical transformations
– Batteries in a flashlight
– Chemical to electrical to light
• Electrical transformation
– Plug in a Blow-dryer
– electrical to heat
• Electrical transformation
– Electric pencil sharpener
– electrical to mechanical
Generating Electricity:
where does electricity
come from?
• Generators: device that spins coiled wire
within a magnetic field producing electricity by
transferring heat energy to mechanical
energy
– The mechanical energy of a spinning turbine is
transformed into electrical energy for human use
– Primary method for producing the electricity in
homes, schools, & the community
Energy Production
• Most Electricity is produced in power
plants by burning fossil fuels to boil
water which produces steam that turns
a turbine to generate electricity.
How a Generator
Works
Power Grid
• A power grid is a transmission
network that connects power plants
to multiple substations near a
populated area.
– Allows distant energy sources (such as
hydroelectric power plants) to be
connected to consumers in population
centers
Power Grid
Transformer
• Device that transfers electrical
energy from one circuit to another
& changes the voltage by
increasing or decreasing it.
– Helps monitor the operation of the
power grid and measures current.
Transformer
Path of Electricity through
a Power Grid
• Power Plant
• Substation ( there are several along the
way)
• Transmission Lines ( high & low voltage)
• Transformer (lowers voltage before
entering the home)
• Junction Box on the home (brings it into
the home)
• Outlet (sends it to electrical devices)
• Electric circuit for a blow dryer