Elenco XP&trade - Manual (Page 7)

Introduction to Electricity
What is electricity? Nobody really knows. We only know how to produce
it, understand its properties, and how to control it. Electricity is the
movement of sub-atomic charged particles (called electrons) through a
material due to electrical pressure across the material, such as from a
battery.
Power sources, such as batteries, push electricity through a circuit, like a
pump pushes water through pipes. Wires carry electricity, like pipes carry
water. Devices like LEDs, motors, and speakers use the energy in electricity
to do things. Switches and transistors control the flow of electricity like
valves and faucets control water. Resistors limit the flow of electricity.
The electrical pressure exerted by a battery or other power source is called
voltage and is measured in volts (V). Notice the “+” and “–” signs on the
battery; these indicate which direction the battery will “pump” the electricity.
The electric current is a measure of how fast electricity is flowing in a
wire, just as the water current describes how fast water is flowing in a pipe.
It is expressed in amperes (A) or milliamps (mA, 1/1000 of an ampere).
The “power” of electricity is a measure of how fast energy is moving
through a wire. It is a combination of the voltage and current (Power =
Voltage x Current). It is expressed in watts (W).
The resistance of a component or circuit represents how much it resists
the electrical pressure (voltage) and limits the flow of electric current. The
relationship is Voltage = Current x Resistance. When the resistance
increases, less current flows. Resistance is measured in ohms (
Ω
), or kilo
ohms (k
Ω
, 1000 ohms).
Nearly all of the electricity used in our world is produced at enormous
generators driven by steam or water pressure. Wires are used to efficiently
transport this energy to homes and businesses where it is used. Motors
convert the electricity back into mechanical form to drive machinery and
appliances. The most important aspect of electricity in our society is that
it allows energy to be easily transported over distances.
Note that “distances” includes not just large distances but also tiny
distances. Try to imagine a plumbing structure of the same complexity as
the circuitry inside a portable radio - it would have to be large because we
can’t make water pipes so small. Electricity allows complex designs to be
made very small.
There are two ways of arranging parts in a circuit, in
series or in parallel. Here are examples:
Placing components in series increases the resistance;
highest value dominates. Placing components in parallel
decreases the resistance; lower value dominates.
The parts within these series and parallel sub-circuits
may be arranged in different ways without changing what
the circuit does. Large circuits are made of combinations
of smaller series and parallel circuits.
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Series Circuit
Parallel Circuit