you have now been introduced to both
voltage and current: two of the key ideas
that underpin electricity However, before
we continue, I just wanted to share spend
one minute sharing with you guys two
quotes which I think are amazing. They're
both from Michael Faraday, a man who
lived in the 1800s, and he played a key
role in the development of electricity. So the first quote is this. So this is in
1850 before electricity was commonplace
and so a British financial minister came
up to Michael Faraday and said, "what use
is this electricity?" and Michael
Faraday, his response was, "well maybe one
day you'll be able to tax it." At this
stage people had absolutely no idea what
all this research into electricity could
lead to and how it could underpin all our
technology today. The second quote
there's a shortened version that I'll
share with you and it is simply, "nothing
is too wonderful to be true." All right
that's enough with quotes for now let's
get back to voltage and current. So
current and voltage are two very
important concepts when it comes to
electrical circuits and I want to share
with you guys the way that I understand
what they are. So for me the key to
understanding current and voltage is to
look at the units of these two
quantities so let's start out by looking
at Amperes, or current. So electrical
current is represented by the symbol I
so it's capital I and it's units are
amperes where an ampere is a Coulomb per
second so an ampere is a Coulomb per
second and to help you understand how
this works I'm going to show you a
simulation. So if we were to have a look at
an actual circuit so here I've got the
circuit simulation that were using
before so the current would be the
number of coulombs that go past a certain
point in the circuit per second so if I
was going to have a look at this part of
the circuit right here
if one Coulomb of charge goes past every
second then I have one ampere of current.
If I had the charge moving twice as fast
so I had two coulombs of charge going
past each second
then I would have a current of two
amperes. So if I had more electrons
moving through a certain point of the
circuit then I would have higher current.
I am now going to show you a formula
that you can use to calculate electrical
current. The formula is I equals Q over T
where I is the electrical current in
amps, Q is the charge that flows through
a point in the circuit measured in
coulombs, and T is the amount of time
that is passed in seconds so you can use
this formula to calculate the current.
Have a go at doing this now.
