Transcript Basic Electricity

Basic Electricity
Electricity is the energy that makes everything from
toasters to televisions work. It is also linked to
magnetism. Together, as electromagnetism, they are one
of the four fundamental forces holding the Universe
together.
• Most electricity is generated in power stations
by magnets that spin between coils of wire to
induce an electric current.
• The magnets are turned by turbines, which are
themselves either turned by steam heated by
burning coal, oil or gas, or by nuclear fuel, or
turned by wind or water.
• The stronger the magnet, the faster it turns,
the more coils there are, so the bigger the
voltage created.
The four basic
concepts we need
electricity as relates to
audio.
• Voltage
• Current
• Resistance
• Power
An electric charge that does not move is called static electricity.
A charge may flow in a current providing there is an unbroken loop, or
circuit.
A current only flows through a good conductor such as copper, namely a
material that transmits charge well.
A current only flows if there is a driving force to push the charge. This
force is called an electromotive force (emf).
The emf is created by a battery or a generator.
Currents were once thought to flow like water. In fact they move like a
row of marbles knocking into each other.
In a good conductor there are lots of free electrons that are unattached
to atoms. These are the ‘marbles.
A current only flows if there are more electrons at one point in the
circuit. This difference, called the potential difference, is measured in
volts.
The rate at which current flows is measured in amps. It depends on
the voltage and the resistance (how much the circuit obstructs the
flow of current). Resistance is measured in ohms.
Voltage
Electric potential difference, potential
drop, electromotive force, electric
tension...
Voltage is commonly referred to as
electrical pressure.
An analogy that is often used is that
voltage is like the pressure of water
which is stored in a dam.
Measured at the base, the water
has tremendous pressure,
regardless of whether or not it is
flowing.
Voltage is the potential for current in the same
way water pressure is the potential for flow.
Voltage is the force
which causes current
to flow through an
electronic circuit. Two
sources of voltage are
batteries and general
power outlets.
Current
• All substances in the universe are made up of
atoms.
• Atoms are made of protons (+ve charge),
neutrons, (neutral charge), and electrons (ve charge). Apparently all of the above are
made of quarks but I've never seen them so...
Who knows. It's not that important in audio.
The electrons are the important thing
here: they collect around the central part
of the atom and the number of electrons
around the atom will give an atom its
overall negative or positive charge.
Nature always seeks balance, and some
types of atoms will "give up" their
electrons easily in order to balance with
other atoms next to them.
That means that some substances conduct
electricity, which is simply electrical charge, easilysubstances like copper, gold, silver. These
substances are conductors.
Some are very stable, and do not give away their
electrons easily, substances like rubber and
plastic. These substances are insulators.
That is why audio and electrical cables
are constructed the way they are.
Electrical current passes along the
conductive element and is contained
within an insulative substance which
protects the outside world from current,
and guides the electricity along the
desired path as well as protecting the
electricity, which is also our audio signal
after all, from interference.
current flow:
Direct current and
Alternating current.
Direct current means
current flows in one
direction, from negative to
positive.
The most common type of
Direct current is used to charge batteries,
and in nearly all electronic systems, as the
power supply. Very large quantities of directcurrent power are used in production of
aluminum and other electrochemical processes.
Direct current is used for some railway
propulsion, especially in urban areas. Highvoltage direct current is used to transmit large
amounts of power from remote generation sites
or to interconnect alternating current power
grids.
Like the difference in height
between the top of the dam and
the bottom, there is an excess
of electrons within the minus
portion of the battery, which is
expressed as voltage (AA
battery is 1.5v for example)
Because its a one way flow,
the charge depletes and runs
out.
Direct current may flow in a conductor such as a
wire, but can also flow through semiconductors,
insulators, or even through a vacuum as in
electron or ion beams. The electric charge flows
in a constant direction, distinguishing it from
alternating current (AC).
The detailed movement of electrons in AC current gets very
complex and depends on the exact conductor being used
but, simplistically, the electrons simply move back and forth
(away from and then towards the generator) over a short
space
If you think of DC as a push system analogous to a straight
flow of water in a hose, then AC is a push-pull system
which would be like water in a hose connected to a
piston that, as the piston cycles, first pushes the water
down the hose and then sucks it back.
In a DC water hose, a molecule of water can only perform work
e.g. moving a turbine, when it travels from one end of the hose to
the other. However, in an AC water hose, a molecule of water just
oscillates around its starting location and it is just the force of the
molecule hitting the next molecule in the chain that transmits the
energy. The last molecule in the chain is always the one that
strikes the turbine and performs the work.
That is why AC can transmit energy over long distances. In DC,
the generator must push an electron all the way down the wire to
the load (and eventually back down the other side of the circuit)
to perform any work. AC by contrast is just transmitting the
electro repulsive force that drive electrons away from each other.
(Just like a Newton's cradle transmits momentum instead of
moving the spheres.)
Fun Facts
Two positive charges repel each other, as do two negative charges. Opposite charges
on the other hand, attract each other.
When an electric charge builds up on the surface of an object it creates static electricity.
You have probably experienced static electricity in the form of a small electric shock,
which is what happens when the electric charge is quickly neutralized by an opposite
charge.
Electric eels can produce strong electric shocks of around 500 volts for both self
defense and hunting.
Electric circuits can contain parts such as switches, transformers, resistors and
transformers.A common way to produce electricity is by hydropower, a process that
generates electricity by using water to spin turbines attached to generators.
Lightning is a discharge of electricity in the atmosphere. Lightning bolts can travel at
around 210,000 kph (130,000 mph), while reaching nearly 30,000 °C (54,000 °F) in
temperature.
Electric fields work in a similar way to gravity with an important
exception being that while gravity always attracts, electric fields can
either attract or repulse.
American Benjamin Franklin carried out extensive electricity
research in the 18th century, inventing the lightning rod amongst
his many discoveries. Lightning rods protect buildings in the event
of lightning by conducting lightning strikes through a grounded
wire.
Back in the 1880’s there was even a ‘war of currents’ between
Thomas Edison (who helped invent DC) and Nikola Tesla (who
helped invent AC). Both wanted their system to be used with AC
eventually winning out due to the fact that it is safer and can be
used over longer distances.
Alternating current is the type available from a
GPO.
Alternating current changes polarity at regular
intervals. House current changes direction 60
times per second. The way in which power
changes direction can be observed on an
oscilloscope and looks like a sine wave of 60
cycles per second or 60Hz. So, "60 cycle hum"
is the sound of AC current leaking into the audio
chain somewhere along the line.
Loads
Why do I have to know about power and
electricity, when all I am doing is mixing music?
Because this can happen.
Uluru gala dinner 31/7/13
To be continued…..