Zener diode symbols.
c. Zener diodes are used in control circuits as reference voltages.
Connecting a zener in series with a resistor and power supply will cause a zener
regulated voltage. Providing that the battery potential is of a voltage greater
than the zener voltage, for any variation of the battery voltage the zener voltage
will remain constant (fig 11).
a. Magnetism, like electricity, is invisible. Its effects, however, are
well known. An example is the attraction of a bar magnet for iron filings. A
magnet has a North pole, designated as "N," and a South pole, designated as "S."
The space around the magnet in which iron filings are attracted is called the
"field of force" or magnetic field, and is described as lines which come out of the
North pole and enter the South pole (fig 12).
OS 010, 1-P6