way that the conductor cuts across magnetic lines of
Q7-4. Which of the following components can act as
force, voltage is generated in the conductor. The
a amplifier or a switching device?
amount of voltage generated depends on the following:
1.
A silicone-controlled rectifier
The strength of the magnetic field
2.
A Zener diode
3.
A bridge rectifier
The angle at which the conductor cuts the
4.
A transistor
magnetic field
Q7-5. Which of the following statement best
The speed at which the conductor is moved
describes a silicon-controlled rectifier?
The length of the conductor within the magnetic
1. It will stop conducting when the gate
field
voltage is removed
The POLARITY of the voltage depends on the
2. It will begin to conduct when a voltage is
direction of the magnetic lines of flux and the direction
applied to the emitter
of movement of the conductor. To determine the
3. A very small gate voltage can be used to
direction of current in a given situation, use the
control high-power requirements
LEFT-HAND RULE FOR GENERATORS.
4. A difference in potential is required
Extend the thumb, forefinger, and middle finger of
between the base and emitter for it to
your left hand at right angles to one another, as shown
conduct
in figure 7-21. Point your thumb in the direction the
Q7-6. A magnetic amplifier uses what type of
conductor is being moved. Point your forefinger in the
voltage to change the permeability of the
direction of magnetic flux (from north to south). Your
magnetic material upon which the coil is
middle finger will then point in the direction of current
wound?
flow in an external circuit to which the voltage is
applied.
1.
A pulsating ac voltage
2.
A dc signal voltage
In figure 7-22 assume the conductor between A
3.
A rectified ac voltage
and B, when moved, cuts the lines of force. This
4.
A pulsating dc voltage
motion induces a voltage between A and B. Because
the conductor completes the circuit, current flows, and
Q7-7. Which of the following statements best
a voltage shows on the voltmeter. The voltage amount
describes the term permeability?
depends on the following three factors:
1. The ability of a substance to allow
The strength of the magnetic field
current flow
2. The ease with which a substance will
MOTION OF
conduct voltage
CONDUCTOR
3. The ability of a substance to become
saturated with magnetic lines of force
CURRENT
4. The ease with which a substance conducts
lines of force when compared with air
GENERATORS
LEARNING OBJECTIVE: Recognize the
operating characteristics of ac and dc
g e n e r a t o r s u s e d i n p ow e r g e n e r a t i n g
equipment.
A generator is a machine that converts mechanical
energy into electrical energy by using the principle of
magnetic induction. The principle of magnetic
induction is based on the theory that whenever a
ASf07021
Figure 7-21.--Left-hand rule for generators.
conductor is moved within a magnetic field in such a
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