BASIC ELECTRONICS - OD1633 - LESSON 1/TASK 2
2.
Series Circuits and Computing and Measuring Voltage
a. The Basic Electric Circuit. The flashlight is an example of a basic
electric circuit. It contains a source of electrical energy (the dry cells
in the flashlight), a load (the bulb) which changes the electrical energy
into a more useful form of energy (light), and a switch to control the
energy delivered to the load.
Before you study a schematic representation of the flashlight, it is
necessary to define certain terms.
The load is any device through which
electrical current flows which changes electrical energy into a more useful
form.
Some common examples of loads are a lightbulb, which changes
electrical energy to light energy; an electric motor, which changes
electrical energy into mechanical energy; and the speaker of a radio, which
changes electrical energy into sound.
The source is the device which
furnishes the electrical energy used by the load.
It may consist of a
simple dry cell (as in a flashlight), a storage battery (as in an
automobile), or a power supply (such as a battery charger).
The switch,
which permits control of the electrical device, interrupts the current
delivered to the load.
b. Schematic
Representation.
The
technician's
main
aid
in
troubleshooting a circuit in a piece of equipment is the schematic diagram.
The schematic diagram is a "picture" of the circuit that uses symbols to
represent the various circuit components; physically large or complex
circuits can be shown on a relatively small diagram.
Before studying the
basic schematic, look at figure 11 on the following page. This figure shows
the symbols that are used in schematic diagrams.
These, and others like
them, are referred to and used throughout the study of electricity and
electronics.
The schematic in figure 12 (on page 28) represents a flashlight. Part A of
the figure shows the flashlight in the off or deenergized state. The switch
(S1) is open.
There is no complete path for current (I) through the
circuit, and the bulb (DS1) does not light. In figure 12, part B, switch S1
is closed. Current flows in the direction of the arrows from the negative
terminal of the battery (BAT), through the switch (SL), through the
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