ELECTRICS EXERCISE: QUESTIONS ONE -CIRCUITS NAME:

1. The deck lights of a vessel connect to a 12 volt electrical system by means of wiring with a maximum current rating of 10 amps. Select the total maximum wattage of deck lights which can be used.

a. 120 watts

b. 60 watts

c. 24 watts

2. Match the following electrical terms with their description.

a. Volt ............. 1. Unit of electrical resistance

b. Amp ............. 2. Unit of electrical power

c. Ohm ............. 3. Unit of electrical current flow

d. Watt ............. 4. Unit of electrical pressure (electro-motive force

3. An open-circuit is a break in an electrical circuit. It will cause the circuit current to rise, usually blowing a fuse.”

TRUE FALSE

4. “An open-circuit increases the circuit resistance to a very high level, and reduces the circuit current to practically zero. It usually stops the circuit operating correctly.”

TRUE FALSE

5 In a series circuit, the total current:

a. splits, and flows separately through each sub-circuit

b. remains the same as it flows through each component in turn

c. will flow through some components if others are open-circuited

“To increase the capacity of batteries, but keep the output voltage the same, they are connected in

SERIES PARALLEL” (Circle the right answer)

ANSWERS ONE

1.         The deck lights of a vessel connect to a 12 volt electrical system by means of wiring with a maximum current rating of 10 amps. Select the maximum wattage of deck lights which can be used.
a.         120 watts
b.         60 watts
c.         24 watts

2. Match the following electrical terms with their description.

a. Volt 4 1. Unit of electrical resistance

b. Amp 3 2. Unit of electrical power

c. Ohm 1 3. Unit of electrical current flow

d. Watt 2 4. Unit of electrical pressure (electro- motive force)

3. An open-circuit is a break in an electrical circuit. It will cause the circuit current to rise, usually blowing a fuse.” FALSE

4. “An open-circuit increases the circuit resistance to a very high level, and reduces the circuit current to practically zero. It usually stops the circuit operating correctly.”
TRUE

5     In a series circuit, the total current:
a.    splits, and flows separately through each sub-circuit
b.    remains the same as it flows through each component in turn
c.    will flow through some components if others are open circuited

6. “To increase the capacity of batteries, but keep the output voltage the same, they are connected in PARALLEL”

QUESTIONS TWO- BATTERIES

1. What could happen if a battery is put in with the polarity reversed?

___________________________________________________________________________________

2. “Battery electrolyte should be kept about 9mm above the top of the plates by topping up each cell with distilled water!” TRUE FALSE

3. “If no distilled water is available to top up a battery, salt water will do as a standby!”

TRUE FALSE

4. “The need for frequent ‘topping-up’ of electrolyte could be caused by an excessive charge rate, or an internal fault!” TRUE FALSE

5. “Corrosion can be easily removed from battery terminals with hot water!”
TRUE FALSE

6. What is the first aid treatment for battery electrolyte burns to the eyes?

___________________________________________________________________________________

7. For the battery arrangements below, state whether they are connected in Series, Parallel, or Series/Parallel, and state their output voltage and capacity (compared to a single battery).

ANSWERS TWO

1. What could happen if a battery is put in with the polarity reversed?
Wrong polarity may cause severe electrical system damage, and injury!

2. “Battery electrolyte should be kept about 9mm above the top of the plates by topping up each cell with distilled water!”

TRUE

3. “If no distilled water is available to top up a battery, salt water will do as a standby!”
FALSE

“The need for frequent ‘topping-up’ of electrolyte could be caused by an excessive charge rate, or an internal fault!”

TRUE

5. “Corrosion can be easily removed from battery terminals with hot water!”
TRUE

6. What is the first aid treatment for battery electrolyte burns to the eyes?
If battery chemicals get into the eyes, immediately flush them gently with clean, fresh, water. Continue gently flushing for at least 20 minutes, and seek urgent medical aid.

7.         For the battery arrangements below, state whether they are connected in Series, Parallel, or Series/Parallel, and state their output voltage and capacity (compared to a single battery)
Left hand Diagram        Batteries Connected in Series
                                                Output Voltage = 24 Volts
                                                Capacity is the same as a single battery

Right hand Diagram      Batteries connected in series/parallel
                                                Output Voltage = 12 Volts
                                                Capacity is twice the capacity of a single                                                       battery

QUESTIONS THREE- GENERATORS & ALTERNATORS

1. If a generator stops charging, number in order the items you would check.

a. Check the regulator for operation (especially mechanical types)

b. Check that the brushes and commutator are not sticking or worn

c. Make sure the drive belt is not slipping

d. Dismantle the generator to check field and armature windings

2. Match each generator regulator component, with its function

              a.   Cut-out                             .........    1         Prevents the generator burning out due to
                                                                                    an excessive charge rate,
              b.   Voltage Regulator .......... 2         Stops the battery discharging through the
                                                                                     generator, when the engine is stopped.
              c.   Current Regulator . ......... 3          Prevents the battery being overcharged
                                                                                     and damaged.

3. If a diode in an alternator should fail, it is likely to cause:

              a.       No output at all from the alternator
            b.       The alternator polarity will be reversed
              c.       The alternator will have a low charge rate

4. “Alternators are capable of operating on either polarity, by simply reversing the battery!”

TRUE FALSE

5. “Although alternators have a long, reliable service life, the alternator diodes are easily damaged by high or reversed voltages, or stray currents due to welding. The battery and alternator should be disconnected when welding!”

TRUE FALSE

6. “Short circuits are most likely to be found where there is exposed wiring or connections, or where wiring may be cut or damaged as it passes through metal casings, bulkheads, etc.!”

TRUE FALSE

7.         Open circuits are best found by checking the most likely causes first. Number the order in which you would check the following things looking for an open circuit.
a.         Plugs and sockets, and flexible cords and cables
b.         Screwed connectors
c.         Fuses and circuit breakers
d.         Wiring looms

ANSWERS THREE

1. If a generator stops charging, number in order the items you would check.

a. Check the regulator for operation (especially mechanical types)

b. Check that the brushes and commutator are not sticking or worn

c. Make sure the drive belt is not slipping

d. Dismantle the generator to check field and armature windings

2. Match each generator regulator component, with its function

              a.   Cut-out                             .........    1 c     Prevents the generator burning out due to
                                                                                    an excessive charge rate,
              b.   Voltage Regulator .......... 2 a     Stops the battery discharging through the
                                                                                     generator, when the engine is stopped.
              c.   Current Regulator . ......... 3 b     Prevents the battery being overcharged
                                                                                     and damaged.

3. If a diode in an alternator should fail, it is likely to cause:

              a.       No output at all from the alternator
              b.       The alternator polarity will be reversed
              c.       The alternator will have a low charge rate

4. “Alternators are capable of operating on either polarity, by simply reversing the battery!” FALSE

5. “Although alternators have a long, reliable service life, the alternator diodes are easily damaged by high or reversed voltages, or stray currents due to welding. The battery, and alternator should be disconnected when welding!”
TRUE

6. “Short circuits are most likely to be found where there is exposed wiring or connections, or where wiring may be cut or damaged as it passes through metal casings, bulkheads etc

TRUE

7.         Open circuits are best found by checking the most likely causes first.   Number the order in which you would check the following things looking for an open circuit.
2         a.       Plugs and sockets, and flexible cords and cables
3          b.       Screwed connectors
1          c.        Fuses and circuit breakers
4          d.        Wiring looms

QUESTIONS FOUR

1. If the Wattage of a vessel’s deck lights are doubled, the electrical wiring will have to carry: (select the correct answer)

a.         four times as many amperes
b.         twice as many amperes
c.         one half the amperes
d.         one quarter the amperes

2. From the list below, select two correct statements.

a.         “Batteries in parallel, are connected negative to negative; positive to positive!”
b.         “Batteries in parallel, are connected negative to positive; positive to negative!”
c.         “Batteries in series, are connected negative to negative!”
d.         “Batteries in series, are connected negative to positive!”

3. Select the best answer. “Circuit breakers and fuses are used to stop:

a.          excessive electrical current flowing in a circuit!”
b.         excessive voltages being accidentally applied to the circuit!”
c.         ‘flashes’ due to lightning strikes getting into the ship’s wiring!”
d.         fatalities caused by severe electric shocks!

4. Select the most likely causes of an electric open circuit.

a.         Damaged insulation due to the rubbing of cables
b.         Fuses, plugs and sockets, flexible cords and exposed connections
c.         Cables packed too tightly into ducts and through openings
d.         Conductors accidentally contacting the ship’s hull

5. Identify the statements below which indicate the precautions you should take with a vessel’s batteries.

a.         No sparks, flames or welding while charging or servicing batteries
b.         Use protective goggles gloves and apron while working with batteryelectrolyte
c.         Keep clean water on hand to flush the skin and eyes if chemical burns occur
d.         All of the above

ANSWERS FOUR

1. If the Wattage of a vessel’s deck lights are doubled, the electrical wiring will have to carry: (select the correct answer)

a.         four times as many amperes
b.         twice as many amperes
c.         one half the amperes
d.         one quarter the amperes

2. From the list below, select two correct statements.

a.         “Batteries in parallel, are connected negative to negative; positive to positive!”
b.         “Batteries in parallel, are connected negative to positive; positive to negative!”
c.         “Batteries in series, are connected negative to negative!”
d.         “Batteries in series, are connected negative to positive!”

3. Select the best answer. “Circuit breakers and fuses are used to stop:

4. Select the most likely causes of an electric open circuit.

a.         Damaged insulation due to the rubbing of cables
b.         Fuses, plugs and sockets, flexible cords and exposed connections
c.         Cables packed too tightly into ducts and through openings
d.         Conductors accidentally contacting the ship’s hull

5. Identify the statements below which indicate the precautions you should take with a vessel’s batteries.

a.         No sparks, flames or welding while charging or servicing batteries
b.         Use protective goggles gloves and apron while working with battery electrolyte
c.         Keep clean water on hand to flush the skin and eyes if chemical burns occur
d.         All of the above