Transcript Electrical Safety

Electrical Safety
& Cells and Batteries
Fulgurites
Lightning can be dangerous because
it discharges so much energy.
Lightning strikes can actually melt
sand and rock when they hit the
ground.
When lightning melts sand &
rock…
It creates glasslined tubes called
fulgurites.
Electrical Safety
January 1998 eastern Ontario and
Quebec were hit by a massive ice storm.
Any person coming into contact with a
power line may create a path for
electricity.
This path is sometimes called short
circuit.
Without a complete circuit…
Electricity cannot
flow.
If electricity can
find another path,
such as through a
person’s body to
the ground, then it
will take that path.
Ice Storm
Dangers of Electrical Shock
Two important aspects of electricity: voltage
& amperage.
High voltage is more dangerous than low
voltage; 50 000 V more likely to kill you
than 10 V.
Even small voltages can kill if the shock
carries a significant number of amps (rate of
flow).
Amps more important than
voltage:
When assessing the potential danger of
electrical shock.
0.001 A passing through your body- likely would
not feel it.
0.015 to 0.020 A- painful shock & loss of muscle
control.
Current as low as 0.1 A can be fatal.
Factors affecting electric
shock:
Current does not flow easily:
Through insulators such as wood, rubber & air.
You might feel just a tingle if you touch an
electrified fence on a dry day when you are
wearing running shoes.
But, you could get a nasty shock if you touch the
fence when you are barefoot in the rain.
Every plug-in device:
Sold in Canada
must have a label
listing what voltage
it requires and the
maximum current it
uses.
The amperage rating does not have to
be high for you to get a shock.
If there is a short circuit or if the
insulation is damaged, you could get a
shock from the electricity before it goes
through the device.
Plugs, Fuses & Breakers
Grounded 3 prong plugs
have an extra wire that
connects the device to the
ground wire of the building.
It provides another pathway
for electricity, just in case
there is a short circuit.
Electricity travels to the
ground instead of through
the user.
Fuses
Interrupt a circuit
when too much
current is flowing
through it.
Contain a thin piece of
metal that is specially
designed to melt if too
much current passes
through it.
Circuit Breakers
Have a special wire that
heats up if there is too
much current.
Hot wire triggers a spring
mechanism that turns off
the switch inside the
circuit breaker.
As soon as problem is
fixed/wire has cooled, the
circuit breaker can be
turned back on.
The danger of lightning
The current in a lightning strike can be as high as
30 000 A, and they can kill.
People can survive lightning strikes when the full
amount of current travels over only part or over
the surface of their bodies.
The danger of lightning
Lightening is a huge amount of negative
charge and tends to seek the highest point on
the horizon to discharge.
Tall buildings are a natural target for lightening
strikes, and so often add lightening rods to their
peaks- lightening rods are connected to the
ground with a wire; discharge is conducted
harmlessly to the ground.