Page 122 - Electromechanical Devices and Components Illustrated Sourcebook

84 Electromechanical Devices & Components Illustrated Sourcebook

Magnetics play an important role in the field of electrome-
chanical devices. The manipulation of magnetic fields pro-
vides an interface between electricity and mechanical compo- +/− Volt Meter
nents. Most transformers, for instance, don’t have an actual − +
electrical connection between their inputs and outputs. They
are instead connected with a magnetic field. Solenoids rely on
a magnetic field, generated by an electrical signal, to produce
motion; while motors derive their rotation through the varia-
tion of magnetic fields.

Electromotive Force Moving Coil

The key to understanding the relationship between electricity,
magnetics, and mechanics is gained through the understand-
ing of electromotive force. Simply stated, electromotive force N
is the electrical energy generated when a conductor is passed
through a magnetic field.
S Magnet
Electrical energy can be generated in two principal ways,
electrochemical and induction. Batteries, as discussed in
Chapter 3, generate electrical energy through the electrochem-
ical process. Generators and transformers utilize induction to
generate electrical energy. Figure 5-1 shows how electrical
energy may be generated with a simple horseshoe magnet and
a wire. A wire loop is connected to a / voltmeter, as shown.
Figure 5-2 Increasing Voltage
The wire is then moved up and down through the magnetic
field. As the wire is moved up, positive polarity is produced
and as the wire is moved down, a negative polarity is pro-
duced. When the wire is repeatedly moved up and down, the
field, the needle will deflect much further than with the single-
needle on the voltmeter will swing to the positive and negative
wire setup. The increase in voltage is directly proportional to the
in direct reference to the direction of the wire movement.
number of turns on the coil. If the coil has 10 turns, it will pro-
To produce higher voltages, multiple loops of wire are moved
duce 10 times the voltage of a single wire.
within the magnetic field. If a coil is connected to the /
In the same way that a voltage can be produced from a
voltmeter, as shown in Figure 5-2, and moved in the magnetic
magnetic field, a magnetic field can be produced with electri-
cal power. If a coil is connected to an electrical power source,
a magnetic field will be generated, as shown in Figure 5-3.
The flux lines show how the field balances in reference to the
coil. When power is connected to the coil, a field is generated.
+/− Voltmeter When the power is disconnected, the field collapses.
− +

Coil
Magnetic Flux Lines

Moving Wire
+ −

N
S N
S Magnet

Battery
Figure 5-1 Inducing Electrical Current Figure 5-3 Flux Lines Surrounding a Solenoid Coil