Transcript What is Electricity1

What is Electricity?
How do we produce Electricity?
What are the different types of
current and how are they
produced?
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What is Electricity
• Electricity involves the
interaction of positive and
negative charges
• Electricity is essentially the
movement of charge
• Electric current is the flow of
charge through a conductor
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Key Electricity terms:
1. Voltage: Force pushing electrons
2. Current: number of electrons
flowing; frequency of e- flow
3. Resistance: how easy or difficult it
is for e- to flow
4. Conductors: have low resistance
5. Insulators: have high resistance
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How do we produce
electricity?
1. Static; friction
2. Generators:
hydroelectric,
nuclear, coal,
natural gas,
biomass, tidal,
hand crank radio
3. Magnetism
4. Solar cells
5. Chemical
reactions;
batteries
6. Piezoelectricity;
using crystalline
flux
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Different types of
Electric current:
• DC= Direct
Current
• This is current
that flows in one
direction from
positive to
negative
charged areas
• AC=Alternating
Current
• This is current
that flows back
and forth,
alternating
direction of flow
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What makes DC?
• Static
discharges
• Batteries
• DC converters/
adapters
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Static Electricity
• Made by the
transfer of
charge due to
friction
• Very dry air
promotes static
electricity, moist
or humid air
reduces it
•Lightening is the
greatest form of
static electric
discharge.
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DC and Batteries
• Batteries use a
chemical
reaction to
produce a flow
of charge.
• Batteries can be
Wet Cell or Dry
Cell in nature
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More about Batteries
• Wet Cells:
• Used in cars,
lawn mowers,
boats
• Often have lead
compound
anodes and
cathodes and
use a liquid
electrolyte
• Maximum voltage
per cell is 2 Volts
• A simple one can
be made with a
copper strip, a zinc
strip and an
electrolyte such as
Hydrochloric acid
or even Lemon
Juice
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More about Batteries
• Dry Cells
• Maximum
• Used in small
voltage per cell
appliances,
is 1.5 Volts
radios, remote
controls
• Often made of a
zinc case and
carbon center
rod and a dry or
paste electrolyte
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Dry Cell types:
• The size AAA,
AA, C, and D
“batteries” that
we use are
single dry cells;
they are not true
batteries
• A battery is 2 or
more cells wired
together
• The maximum
voltage available
from any single
dry cell is 1.5
volts, so why so
many different
types.
AAA=1.5V
D=1.5V
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More about batteries
and single cells:
• So how is a 9V
built?
• How does a car
battery have 12V?
• How does a
camping lantern
battery have 6V
while the same
size hobby battery
has 1.5V?
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More about batteries
and single cells…
• A 9V battery has 6
smaller dry cells in
it
• A car battery has 6
smaller wet cells
• A lantern battery
has 4 dry cells
wired in series and
a hobby battery
has 4 dry cells
wired in parallel 13
Good and Bad of Wet
and Dry cells:
•
•
•
•
Wet Cells
Bad: often use acid
electrolytes
Bad: tend to be
large
Good: can be
recharged
Good: produce
more Voltage per
cell
•
•
•
•
Dry Cells
Bad: cannot be
recharged
Bad: only produce
1.5 Volts per cell
Good: some can be
recharged
Good: smaller and
lighter and usually
do not corrode
appliance
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DC Adapters
• Used to convert AC
to DC for appliance
use
• Range in sizes from
very small Voltages
to very large
voltages
• A telephone may
use 9 V while a
laptop computer
often uses 18 V
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What makes AC?
• Generators:
change
mechanical
energy into
electrical energy
with the use of
magnets
• It is available
through any wall
outlet
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How does a generator
work?
• A generator
turns a magnet
in between coils
of wire and the
magnetic field
induces an
electric charge
flow in the coils
of wire
• Different
directions of
current flow are
created as the
magnet turns
causing the
direction
changing
characteristic of
AC
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More about AC
• AC is produced at
certain
frequencies of
cycles due to the
spinning of the
magnets in the
generators used
• The frequency of
these cycles
varies around the
world
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AC Stats.
• The U.S.
produces AC at
60Hz (cycles per
second) and
household outlets
are 120 Volts and
large appliance
outlets are 220 V
• The UK is at
50Hz and 230V
• Japan is at
50/60Hz and
100V
• Australia is at
50Hz and 230V
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Problems with travel and
different AC frequencies
• If you purchase an
appliance that is only
set to US it will not
work in most other
countries
• The plugs are not the
same either
• You would need to
purchase a set of
adapter plugs and
purchase appliances
that are adaptable
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Possible Pros and Cons of
AC and DC
• Pros: AC is
easier/cheaper
to produce and
control in large
quantities
• Pros: DC is
needed for many
electronic
components and
it is easy to
transport
• Cons: AC
production
requires a
generator and
other supplies
• Cons: DC
batteries are
expensive and
have a limited
lifespan
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