electrical theory and distribution

Question 1

Current (I)

Answer 1

flow of electric charge, measured in amperes or amps

Question 2

Voltage (V)

Answer 2

a difference in electric potential. measured in volts

Question 3

resistance (R)

Answer 3

an electrical circuit’s opposition to the flow of current. measured in ohms

Question 4

conductor

Answer 4

little resistance to current (silver, copper, iron, etc.)

Question 5

insulator

Answer 5

high resistance to current (wood,paper, plastic, etc.)

Question 6

Ohm’s Law

Answer 6

current in a circuit is directly proportional to the applied voltage, and inversely proportional to the circuit resistance V=IxR

Question 7

Faraday’s Law of Induction

Answer 7

3 requirements to produce current: magnetic field, conductor, motion between the conductor and magnetic field. when a permanent magnet is moved relative to a conductor (or vise versa) an electric current is produced

Question 8

Direct current (DC)

Answer 8

current flows in one direction and is of constant magnitude. Produced by: battery, DC generator, AC to Dc conversion, solar panel. Measured in Volts

Question 9

Alternating Current (AC)

Answer 9

Cycles, direction and magnitude of current in an AC circuit will periodically change. Measured in Volts and frequency (Hz). Frequency is the number of cycles per second. Function of time, sine wave

Question 10

Alternating current generator

Answer 10

Conductor loop rotates in magnetic field. slip rings rotate with the conductor loop. Stationary brushes ride against the slip ring. voltage generated across brushes

Question 11

AC vs DC

Answer 11

AC POWER: easier to generate, uses less complex equipment, voltages can be raised w/ a transformer, cannot be stored in a battery.
DC POWER: can be stored in battery, cannot raise or lower voltages w/ a transformer

Question 12

Ship electrical power distribution

Answer 12

Generators, switchboards, load centers, distribution panels, circuit breakers, fuses, loads

Question 13

Electrical generators

Answer 13

Convert mechanical energy into electrical enegery. powered by steam turbines, gas turbines, diesel engines, electric motors

Question 14

switchboards

Answer 14

contains controls for the production, regulation, and distribution of electricity. distribute electricity to shipboard equipment. house bus-work, circuit breakers and fuses. Receive electricity from generators

Question 15

Excessive electric current

Answer 15

Causes: reduced component lifespan, component failure, electrical fire.
Protection devices: circuit breakers, fuses

Question 16

Circuit breakers

Answer 16

opens at various set points (currents) protects generators & equipment. Operated Manually (locally) or Electrically (remotely) changes the electrical plant configuration. Isolates equipment and are reusable

Question 17

Fuses

Answer 17

encased this metal wire, high current (heat) melts the fuse. Causes an open circuit. Protects the circuit/equipment from excessive current. Single use. replace “blown” fuses

Question 18

Vital Equipment

Answer 18

Required for safe operation of a ship. Multiple power sources. Power source shifts to continue operation during casualy. (firefighting pumps, stering gear, weapon systems)

Question 19

Non-vital equipment

Answer 19

Not required for safe operation of a ship. Ex: laundry equipment, galley. Not preferentially powered during casualty. conserves power for vital equipment

Question 20

Personal Protective Equipment (PPE)

Answer 20

Rubber gloves, face shield, rubber matting, remove all conductive clothing (belt,watch, necklace…)

Question 21

Electrical fires

Answer 21

secure power, battled with CO2. don’t use water stream: electrocution hazard, prevents further damage

Question 22

.001 amps = 1 milliamp

Answer 22

tingles sensation

Question 23

.01 amps = 10 milliamps

Answer 23

severe shock, uncontrolled muscle spasms

Question 24

.1 amps = 100 milliamps

Answer 24

DEATH

Question 25

DANGER TAG

Answer 25

operation will cause injury, death or equipment damage. Equipment shall NOT be operated

Question 26

CAUTION TAG

Answer 26

Used as a precautionary measure. provides temporary special instructions for equip. Ahere to specific instructions

Question 27

Electronic equipment maintenance

Answer 27

De-energized AND mark with DANGER TAG. Energized equipment REQUIRES CO authorization and safety observer

Question 28

Writing a tag

Answer 28

Requires 3 people. 1st person: identifies scope of work, writes tags to isolate work boundaries. 2nd person: Verifies the scope of work, ensures the tag adequately isolates the work boundaries. 3rd person: Officer to verify and approve hanging

Question 29

Hanging a tag

Answer 29

1st person: Places valve/breaker in correct position, hangs tag. 2nd person: independently verifies, valve/breaker in correct position, tag is on correct equipment. Officer authorizes work