Electrical Power Video Lecture - Physics for EmSAT Achieve

let's talk about power now not that kind
of power electric power it takes energy
to light a light bulb and it takes
energy to move hundreds of pounds in
both cases though the rate at which that
energy is used is called power let's go
back to our weightlifter it turns out
that moving heavy objects makes for a
great example of explaining power moving
a hundred kilograms through the air
requires you to spend a good deal of
energy however moving the same 100
kilograms across the same distance more
quickly requires the same amount of
energy but you need more power in the
1780s the Scottish inventor James Watt
greatly improved the design of the steam
engine which helped bring about massive
advancements in the Industrial
Revolution he also coined the term
horsepower to compare the output of
steam engines with the power of draft
horses thanks to all that the SI unit
for power is now the watt I mentioned
that power is a rate much like speed is
a rate for example miles per hour or
kilometers per hour tells you how far
you've traveled for a given amount of
time a watt is equal to one Joule per
second and it shows how much energy is
spent or transferred with respect to
time for example if it takes three
seconds to expend 900 joules of energy
to move away over your head you'll need
300 watts of power now if you spent the
same amount of energy lifting the same
weight but did it in only one second
you'd need 900 watts of power you can
actually try this yourself try taking a
heavy object like this dumbbell here and
moving it about 1 meter in the air but
make it take about 3 seconds now try
moving that same object the same
distance but do it in one second you'll
notice that it takes a lot more effort
on your part
athletes often refer to this as
explosiveness doing a movement or moving
a heavy object very quickly with that
understanding of power let's see how
this relates to electric power I've
already mentioned that one watt is equal
to one Joule per second we know that the
vault is equal to one Joule per Coulomb
and the ampere is one Coulomb moving
past a point per second if we were to
multiply
biovolt times an ampere we could cancel
out the Coulomb units and we'd get one
Joule per second hey that's the
definition of a watt so we can safely
calculate electric power as voltage
times current let's try this with an
example
once again I've hooked up a resistor to
my trusty power supply and cranked up
the voltage to about three point zero
three volts we can see that about point
zero three amps are flowing through the
circuit and with that information we can
calculate electric power using our
equation from earlier P equals V times I
we can plug in three point zero three
volts and point zero three amps with
some multiplication we can see that the
resistor is consuming point zero nine
zero nine watts what do we mean by
consuming power
well since energy can neither be created
nor destroyed it's not really fair to
say that something is consuming power
like you're eating it however when we're
talking about power consumption in terms
of electrical component we really mean
the ability of that component to convert
electrical energy into some other form
of energy in the case of our resistor
electrical energy is being converted to
heat all atoms vibrate randomly and that
vibration corresponds to the temperature
of the material the more the atoms are
vibrating the hotter the object is now
as electrons move through a material
like copper wire they will ultimately
bump into some of the atoms which causes
the atoms to vibrate even more this
results in the material heating up if
resistors are made specifically to cause
more of these collisions and therefore
restrict the flow of current but it also
means that they get hotter the more
current they impede this is a rather
large 8 ohm resistor and this is an
infrared thermometer that lets me read
the surface temperature of objects at a
distance right now there's no
electricity flowing through the resistor
and it's reading about twenty four point
five degrees Celsius if I apply eight
volts across the leads about 1 amp will
flow through it resulting in about eight
watts being converted to heat now if we
measured again we see that the surface
temperature has risen by about four
degrees that's the magic of energy
conversion we can use all that heat for
something useful what I've got here is
an Incan
light bulb and in it is a very special
resistive element known as a filament
when the filament gets hot enough it
begins to emit visible light so when I
give it some electric current I get
light after a while though the bulb gets
hot to the touch as a result of
restricting all that current and as it
turns out incandescent bulbs are very
inefficient as most of the electrical
energy is converted to heat
not light we can use the heat from
resistors for other purposes however
most toasters rely on resistive elements
to turn bread into crispy toast some
space heaters use a similar element to
keep your legs warm on a cold winter day
and older electric stoves also rely on
resistance to convert electricity to
heat in order to cook your dinner so
remember your electrical devices aren't
consuming power in the sense that
they're eating it but they're converting
electrical energy into something else
like keep motion or sound speaking of
eating I need to convert some electrical
energy to heat to make myself some lunch