e. We have seen that a magnetic field, made up of lines of force, is
created around a wire when current is passed through it. If a magnetic field is
moved so that the lines of force cut across a wire conductor (fig 16), a voltage
will be induced in the conductor. The induced voltage will cause current to flow
when an electrical load, such as a resistor, is connected across the conductor.
Figure 16.
Magnet field moving about a wire.
(1) The direction of current flow is determined by the direction of the
magnetic lines of force and the direction of motion of the magnetic field with
respect to the conductor. To visualize this, note the illustration (fig 16).
Magnetic pole pieces are being moved so that the magnetic lines of force are
cutting across a conductor.
(2) The direction of the magnetic lines of force is upward, since
magnetic lines leave the North pole and enter the South pole. The direction of
motion of the magnetic field is toward the right, as indicated by the arrows. With
this direction of motion, the magnetic lines are striking the conductor on its left
side,, which is called the leading side.
(3) The direction of current flow can be determined by applying the
Right-Hand Rule as follows: grasp the conductor with the right hand with the
fingers on the leading side of the conductor and pointed in the direction of the
magnetic lines of force. The thumb will then point in the direction of current
flow (fig 17).
Figure 17.
Application of Right-Hand Rule.
(4) Voltage is generated in Delcotron generators by moving strong
magnetic fields across stationary conductors.
f. Although this coverage of basic principles has been limited and rather
brief, it will serve as a useful background for the next paragraph covering the
operating principles of generators.
5.
GENERATOR OPERATING PRINCIPLES.
a. In the review of electrical fundamentals, it was observed that a voltage
will be induced in a conductor when a magnetic field is moved across the conductor.
For example, consider a bar magnet with its magnetic field rotating inside a loop
of wire (fig 18). With the magnet rotating as
OS 010, 1-P8
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