Electricity

Knowledge of the basic principles of electricity is necessary for understanding

lighting circuitry, electrical distribution, power consumption, operating costs,

switch control, and dimming control.

Principles of Electricity

Electrically charged particles called elec-
trons, which orbit the nucleus of an atom,
can be made to flow from one point to
another. This is observable in objects
charged by friction and in natural phenom-
ena: lightning is a huge spark of electricity.
A flow of electricity is called anelectric
current; the rate of flow of an electric current
is measured in amperes (amps, A). The
potential of the flow of electricity is calledvolt-
age; it is measured in units calledvolts(V).
Water provides a helpful analogy to
these concepts. The amount of pressure
that moving water exerts inside a pipe is
analogous to volts; amperes are similar to
the “gallons-per-second” measurement, the
rate at which water passes through the pipe.
The pipe is the conductor or wire, the wall of
the pipe is the insulator, and the faucet is
the resistance or dimmer. The larger the
pipe, the greater the flow it can carry.
The path through which an electric cur-
rent flows is called acircuit. When no gap
exists in the path, it is called acomplete cir-
cuit(figure 11.1). When a gap occurs, it is
called abreak in the circuit.

Resistanceimpedes the flow of current

and is determined by the composition of a

material. This results in the production of

light or heat or both. Aresistoris a device

placed in the path of an electric current to

produce a specific amount of resistance. If

electricity flowing along a path is slowed by

11

Figure 11.1Complete circuit.