Transcript Electrostatics and Electricity

Electricity
What is electricity?
• Electric current – flow of electrons through
a _______
• Current (I) is measured by how many
__________pass a given point during
each second
• Ampere – amount of current that flows
past a given point in _________
What are parts of an electric
circuit?
• A source of ________
• Load or _________
• Wires
• Switch
Sources of electrons
• Electrochemical cell
_____________ causes a flow of
electrons
Two types
_____cell – batteries in your Ipod
_____cell – car battery
• Generator – the current running through wires in your
house
_________
_______________
____________
Load or resistance
• Load – device that uses the electrical
energy
Light bulb, heating coils in a toaster,
microwave oven
• The load provides _________ to the flow
of electrons
• Electrical energy converted into _____,
_______, or _________ energy
Wires
• Wires provide a _______ for electrons to flow
• Based on being good conductors
Conductors – materials that electrons can
move through ________
ex. – copper, gold, silver
• Other materials are insulators
electrons ________move through easily
ex. – wood, cotton, rubber, glass
Why are wires covered with
insulating material?
• Two reasons
So electricity running through wires
can’t be _______________
So wires can’t touch each other and
______________ – causing a fire
What is relationship between
current, voltage, and resistance?
voltage = current x resistance
current : units are _______
voltage : units are _______
resistance: units are ______
V
I R
Try a problem
• What is voltage if current is 1.5 amperes
and resistance is 30 ohms?
Second problem
• What is current flowing through a wire if
the resistance is 20 ohms and the voltage
is 40 volts?
Third practice problem
• What is a wire’s resistance if a current of
0.5 amperes flows through a wire and the
voltage is 50 volts?
What is direct current?
• Electrons flow from _____ terminal to
________ terminal
• Examples:
AAA batteries
Car battery
Battery charger
What is alternating current?
• Electricity changes direction ________
• Changes direction at speed of about
____times per second
• Electric energy is transferred. Electrons
__________
• Advantage
Can travel over ______ distances at
high _______
How is electrical power charged to
your house?
• First calculate electric power in watts
voltage x current = power
• Then multiply watts by hours, and divide
by 1000 to get kilowatts
• Unit for electric energy is usually _______
One kilowatt of power being used for 1
hour
Practice problem
• A clothes dryer power usage is 4000 watts
• How much energy in kilowatt hours is used
if a dryer is used for 30 minutes?
Electrical safety
• Voltage __________ is what can hurt you.
• If your hands and feet are dry and you touch a
source of electric house current, then there is
120V difference between the source and the
ground you are standing on
• Lot of ___________since dry – not much
_________flows
• What if feet are wet? Resistance _____ and a lot
of current can flow