Electricity is vital to our civilization. So what is electricity and how does it work? To explain electricity we need to zoom passed
the molecular and into the atomic level. Atoms are the smallest things we can kind
of see, but not with the naked eye: Only with a scanning tunnelling microscope can we get
a glimpse of somewhat fuzzy spheres. To really understand electricity, we must
go even further and look inside an atom. This is where it gets complicated, because
the inside of an atom cannot be seen, at least not at the time of writing. So, we’ll use this representation of the
inside of an atom. This is called the Bohr-model, keep in mind
that it is not to scale, and only two-dimensional. This model is also known as the planetary
model, modelling the parts of an atom as planets orbiting a sun – or moons around a planet. While actually, these orbiting moons are not
at any one place at any one time at all, but exist more as regions, or clouds, around the
core. However inaccurate the Bohr-model might be,
it will do for our explanation of electricity. Atoms consist of protons and neutrons, these
form the nucleus of the atom. Orbiting the nucleus are the electrons. It’s these electrons that are responsible
for electricity, hence the name. Think of these orbits more as shells, surrounding
the nucleus. What type of atom – which element – it
is, is defined by the number of protons in the nucleus, at the centre. Atoms of one element all have the same number
of protons, but can have different numbers of neutrons and electrons. It’s this variable number of electrons,
that is important to our understanding. Electrons – which are far lighter than the
protons in the nucleus – can relatively easily move. And this is important, because the movement
of electrons is what forms an electric current. The atom’s protons account for the positive
charge of the nucleus, and the electrons for the negative charge. In a stable, resting, or rather, neutral electrical
condition, these charges balance each other out within the atom. This gives the atom a net electric charge
of zero, for each positive proton you will find one negative electron. In this state the atom is at its lowest possible
energy level, which we call the ground state of the atom. However, we can change the atom’s charge,
or energy level, by causing it to gain or lose electrons. When the atom has fewer electrons than protons,
it becomes positively charged. But when the atom has more electrons than
protons, the net charge swings back the other way, and it becomes negatively charged. More electrons than protons mean the atom
is negatively charged, fewer electrons than protons mean it is positively charged. Losing or gaining electrons changes the atom’s
electric charge. The remainder of this video we will colour
code the atoms, as follows: A positive charge – or absence of electrons
– is represented with red. A negative charge – a surplus of electrons
– is represented with blue. A neutral charge – or a balance between
electrons and protons – is represented by a blend of red and blue: Purple. So, when in a ground state or uncharged, it
looks like this – and it’s called an atom. When charged, negatively or positively, it
looks like these. Instead of atoms, when there is a charge,
they are called a negative or positive ion. Each shell of an atom can hold a maximum number
of electrons. The inner shell can hold 2 electrons, the
second can hold 8, the third 18, and there are elements with all seven known shells. Shells are populated with electrons from the
inside out. Meaning that added electrons always go for
the inner-most shell possible with a spot left. The number of electrons on the outermost shell
determines the reactivity of the atom. This shell is called the valence shell, and
its electrons are called valence electrons. When the outermost shell is full, the atom
is generally stable and least reactive. You may be familiar with the term and effects
of static electricity. When you, for instance, shuffle your feet
over a nice, soft carpet… …you build up a positive charge, because
negatively charged electrons are being lost to the carpet. Carpets are often made from a material with
the properties of an insulator. Insulators do not easily give up electrons
but can get a local charge when electrons from a conductor are rubbed off on them. These electrons will just sit there until
something else takes them away. An insulator’s valence shell is already
quite full of electrons. However, your body is a conductor. Conductors have loosely bound valence electrons
which are easily transferred or lost, in this case from your body to the area of the carpet
where you’re shuffling. Instead of you and the carpet having a neutral
charge, a charge imbalance is being created between you and the carpet. Now, when you touch a metal object, for instance
a door knob, you get zapped. The door knob may be neutrally charged: it
is metal. And, metals too, are conductors, with loosely
bound electrons on the outer shells of their atoms. These electrons immediately move to your body
to restore the charge imbalance, giving you a jolt. Nature always seeks a neutral charge equilibrium,
a net charge of zero. Materials with high electron mobility, are
called conductors. Materials with low electron mobility, are
called insulators. A commonplace object where you can see an
insulator and conductor working together, is in a simple wire. This electrical wire has a copper core and
a plastic shell. Copper atoms have a very loosely bound electron
on the outside, as seen here again using the Bohr-model. This makes copper a perfect conductor, whereas
the plastic is an insulator. The millions, if not billions, of copper atoms
in this piece of wire, easily exchange electrons, allowing us to make an electrical circuit
with it. Think of an electrical circuit as a path that
connects two points with a possible charge imbalance, usually connecting a negatively
charged point to a positively charged. Like marbles in a tube moving from a high
place full of marbles to a low place lacking marbles. Imagine these marbles all along the circuit,
each marble being an electron. These marbles originate from a power source,
for instance a battery. And we’ll explain how batteries work exactly,
in a future video. Electrons move from the negative to the positive,
as we’ve established earlier. The battery pushes out electrons from one
end and attracts them from the other. As one is pulled in, one is pushed out. Despite the electrons moving relatively slowly,
this effect causes the energy to be transferred almost instantaneously. To create such a flow of electrons, we must
provide them a path with a conductor, such as the copper within our wire. If this path is blocked by an insulator, such
as plastic, rubber, or air in the case of a cut wire, the electrons cannot continue
to flow – stopping the electric current. The key to the flow of electricity is making
a continuous electrical circuit. Connecting a wire between a source of electrons,
and an attractor of electrons. All electrical devices are powered this way,
that is why your battery has two poles: A source and an attractor, a negative and a
positive. This is also why your electrical plug has
at least two tongs, one for incoming electrons, one for outgoing. You see, electrons are not spent, they do
not cease existing: They are mere carriers of charge and can only be useful on their
way to their destination. Take note, that connecting two poles of a
power source directly, can actually be very dangerous(!) This is what’s called a short circuit, because
there is nothing between the source and the destination of electrons, to power, such as
a lamp or television. This means that the electron flow will not
encounter any resistance. The release of energy, when short circuiting,
is there for instant, often paired with the involved wire heating dangerously. This is why buildings and some devices, have
fuses, these automatically cut the current flow, when the current becomes too high, preventing
damage or worse: Fire. In the next videos on electricity, we’ll
learn more about generating power, resistance, voltage, amperes, batteries, fuses, motors,
transformers and more. Subscribe and hit that bell to get notified
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