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Module 1—Introduction to Matter, Energy, and Direct Current
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from short-circuit current is accomplished by use of fuses and other
circuit protection devices.
A VOLTAGE DIVIDER
is a series circuit in which desired
portions of the source voltage may be tapped off for use in equipment. Both negative and positive voltage can be
provided to the loads by the proper selection of the reference point (ground).
ELECTRICAL SAFETY PRECAUTIONS
must be observed. A fatal shock can occur from 0.1 ampere
of current. Voltages as low as 30 volts have been recorded as causing sufficient current to be fatal.
ALL LIVE ELECTRICAL CIRCUITS
shall be treated as potential hazards at all times.
ELECTRONIC or ELECTRICAL EQUIPMENT
discovered to be faulty or unsafe should be reported immediately to
ELECTRICAL or ELECTRONIC EQUIPMENT
should be used and repaired by authorized personnel only.
A CO2 EXTINGUISHER
should be used to
extinguish electrical fires.FIRST AID for ELECTRICAL SHOCK
includes the following
Remove the victim from the source of the shock.
Check the victim to see if the person is breathing.
If the victim is not breathing, give artificial ventilation. The preferred method is mouth-to-mouth.
CPR may be necessary if the heartbeat has stopped, but do not attempt this unless you
have been trained in its use. OBTAIN MEDICAL ASSISTANCE AS SOON AS POSSIBLE.
ANSWERS TO QUESTIONS Q1. THROUGH Q61.
A1. (a) DS1, the flashlight bulb (b) BAT, the dry cell
A2. The path for current is incomplete;
or, there is no path for current with S1 open.
A3. A schematic diagram.
A4. (a) Current increases (b) Current decreases
(a) Current decreases (b) Current
A7. 1.25 amperes.
A8. 4 amperes.
A10. By changing the circuit resistance or
the voltage of the power source.
A12. 6 amperes.
A13. A wirewound resistor.
A14. 1 kilowatt.
A15. 8,952 watt hours or 8.952 kWh.
A16. 942 (rounded to 3 places).
(a). 160 ohms
(b). 480 ohms
E1 = 60 volts
E2 = 180 volts
E3 = 240 volts
E1 = 80 volts
E2 = 240 volts
E3 = 320 volts
A20. The source voltage would have to be
increased to 640 volts.
(a) 330 ohms
(b) E1 = 150 volts
E2 = 18 volts
(c) 1.98 kilowatts
(d) P1 = 900 watts
= 1.08 kilowatts
A22. The point at which current enters the resistor is assigned a negative polarity and
the point at which current leaves the resistor is assigned a positive polarity.
A23. 2 amperes. A24. 120
A27. A circuit where there
is no longer a complete path for current flow.
A28. An accidental path of low resistance which passes an
abnormally high amount of current.
The internal (source) resistance of the battery will drop some of the voltage.
A30. When the load
resistance equals the source resistance.
A33. 60 volts.
A34. Total current in a series circuit flows through every circuit component but in a
parallel circuit total current divides among the available paths.
A35. Whether the current is entering
the junction (+) or leaving the junction (-).
A39. Equivalent resistor or Req.
A40. In both cases all the power used in the circuit must come from the
A42. PT = 60 W, ER2 = 10 V.
A45. Because of the 2-volt drop across the internal resistance, only 48 volts is available for the
rest of the circuit.
A46. (a) Total resistance increases, total current decreases (b) Total resistance
becomes infinite, total current is equal to zero
A47. (a) Total resistance decreases, total current
increases (b) Total resistance decreases, total current increases
A49. The source voltage and load requirements (voltage and current).
45 mA rule-of-thumb.
A52. 495 mA.
A53. R1 is the bleeder resistor. Bleeder current must be known before any of the remaining
divider resistor ohmic values can be computed.
A54. (a) By adding the bleeder current (IR1) and the
current through load 1(b) By subtracting the voltage of load 1 from the voltage of load 2.
A55. 1.35 watts.
A56. The series-parallel network drops the remaining source voltage and is used to take
the place of a single resistor (75 ohms) when the required ohmic value is not available in a single resistor.
= 2 watts; R5
= 6 watts.
A58. The ground (reference point) is placed in the proper point in the voltage divider so that positive and
negative voltages are supplied.
A59. NEVER! All energized electric circuits should be considered
You should immediately report this condition to a qualified
A61. Only trained, qualified personnel.
Introduction to Matter, Energy, and Direct Current,
to Alternating Current and Transformers, Introduction to Circuit Protection,
Control, and Measurement
, Introduction to Electrical Conductors, Wiring Techniques,
and Schematic Reading
, Introduction to Generators and Motors
Introduction to Electronic Emission, Tubes, and Power Supplies,
Introduction to Solid-State Devices and Power Supplies
Introduction to Amplifiers, Introduction to
Wave-Generation and Wave-Shaping Circuits
, Introduction to Wave Propagation, Transmission
Lines, and Antennas
, Microwave Principles,
, Introduction to Number Systems and Logic Circuits, Introduction
to Microelectronics, Principles of Synchros, Servos, and Gyros
Introduction to Test Equipment
, Radar Principles,
The Technician's Handbook,
Master Glossary, Test Methods and Practices,
Introduction to Digital Computers,
Magnetic Recording, Introduction to Fiber Optics