A 5 V DC source has an internal impedance of 0,2 ohms. When a load of 2,3 ohms is applied what voltage will be measured at the source terminals?
A triac is used to provide temperature control of an oven. The galley complain that the oven only reaches approximately 50 % of demanded temperature. Which of the following is a likely cause?
The triac has completely failed.
Connection between the demand knob and the triac gate terminal has gone open circuit.
One of the main switching elements in the triac has failed.
The voltage supply to the oven controller is reduced by about 50 %.
Which of the following measures is to be taken when working with batteries?
Add new acid electrolyte to batteries that are in use.
Keep the batteries in discharged state.
Recharge batteries immediately after discharge.
Install alkaline and lead-acid batteries in the same compartment.
Which of the following is an application of a piezoelectric sensor?
What is the minimum starting requirement of an emergency generator?
1 set of starting device with stored energy capable for at least 3 consecutive starts.
2 separate starting devices each with stored energy capable for at least 3 consecutive starts.
2 separate starting devices each with stored energy capable for at least 4 consecutive starts.
3 separate starting devices each with stored energy capable for at least 3 consecutive starts.
When considering instrumentation systems, what is the meaning of the expression “dead-band”?
The controller will enter “sleep mode”.
The controller will is not respond to adjustment of set-point.
It will take some time before the controller will react to a change.
The controller will not react to a process change in this range.
Which of the following is the minimum acceptable value of insulation resistance for High Voltage equipment?
In tanker operations, there will be some areas and zones where flammable or explosive vapour, gas or dust may be expected. Such areas are classified as hazardous. What is meant by hazardous area Zone 1?
Flammable mixture is not present at all times.
Flammable mixture would not normally be present or it would be present for a short period only.
Flammable mixture is continuously present or present for long periods.
Flammable mixture is not continuously present, but will be present during normal operations.
Which of the following methods may a diode be tested by?
Use a Digital Multi-Meter set to measure ohms in forward and reverse directions.
Connect to low ohms resistance tester.
Use a Digital Multi-Meter set to check forward voltage and reverse current blocking.
Use an insulation resistance tester (Megger).
When performing electrical testing of a three phase motor, insulation resistance measurements may be influenced by which of the following?
Humidity, frequency and dampness.
Humidity, pressure and surface contamination.
Temperature, humidity and surface contamination.
Temperature, pressure and dampness.
Flow irregularities in pipes are not caused by:
Which of the following is not a mode of a closed loop control?
A Multimeter is not suitable to measure:
Continuity testing of a delta connected three phase induction motor yields the following results; U1-V1 = 4 ohms, V1-W1 = 4 ohms, W1-U1 = 4 ohms. What is the value of continuity resistance for each winding ie. U1-U2?
Which of the following functions does the diode shown here perform?
Return inductive current to supply at switch off.
Allow Op Amp to top up +15 V rail.
Reference the transistor to +15 V.
Provide an overload route for transistor current.
Which of the following is an application of an capacitive sensor?
Some ships generate electrical power at 440 Volts, but then step up this voltage to supply specific electrical equipment. One common example, may be to feed a large bow thruster. Why is this done?
Manufacturers can supply High Voltage bow thrusters at less cost, and the power factor is improved.
A large bow thruster will draw very large currents at low voltage. Being typically remote from the generator, significant voltage drops would occur at low voltage.
The shipyard could not purchase High Voltage generating plant at the time of manufacture, so they used what was available at the time.
The overall ship’s electrical load does not justify High Voltage generating plant. This method allows more power to be delivered to the bow thruster at low running cost.
In an automatic temperature control system, operating with a PID controller which of the following settings or parameter adjustments may result in system oscillation?
What are the main elements for Process Control?
Sensor, Controller, Noise, Final Control Element.
Process, Sensor, Final control element and Controller.
Resistor, Capacitor, Battery, Load.
Sensor, Modulation, Controller, Process.
Following shows circuitry of a peak detector. What is the output voltage curve, Vo if Vi is a sinusoidal input curve?
Vo will peak when Vi is at the maximum, remain constant and fall to zero when Vi becomes negative.
Vo will spike when Vi is at the maximum/minimum point of the sinusoidal curve; zero everywhere else.
Vo will peak at a level less than Vi maximum voltage and remain constant throughout.
Vo will be the same sinusoidal curve but at a lesser amplitude.
When selecting switchgear to work with High Voltage it is important to use an appropriate arc quenching medium. What is meant by arc quenching medium?
A material which assists a welding process.
The gas, liquid or vapour which will minimise creation of an electric arc as contacts open.
The way in which the contacts separate as the switchgear operates.
Equipment which communicates information about the arcing.
A 250 V contactor has been fitted to a 220 V supply. Which of the following symptoms might be observed?
Contactor chattering (vibrating).
The circuit shows a transformer with two windings, N (1) = 2 000 and N (2) = 1 000 turns, on a common magnetic circuit. Assume that there are no energy losses in the transformer itself. Calculate the output voltage V (2) when the input voltage is V (1) = 100 Volt.
This circuit consists of a current source I, a change-over switch S, a resistor R and a capacitor C. The current/time figures 1 to 4 show possible changes in the current I when the switch S is suddenly shifted from position 1 to 2 at time t = 0. Which diagram is correct?
Which cell voltage is required to trickle charge a lead acid battery?
When the cable length exceeds approx. 10 meters we normally have to in case of a Pt 100, in some way compensate for the cable resistance. Do we also have to do this if we choose to use a T802 temperature sensor?
Depends on temperature to be measured.
High Voltage systems rely on the installed protective equipment being able to interrupt any fault in the system. Throughout the system, the fault level has been calculated, and under no circumstances must the system be modified to exceed this fault level. What is meant by fault level?
The amount of apparent power, that would be drawn from the generating plant, when a short circuit occurs at the bus bars.
The current level flowing into a symmetrical short circuit fault between all three phases.
The amount of apparent power that could flow into any fault at any.
The current level flowing into a dead short to earth at any point on the ship, directly from the High Voltage system.
The continuity resistance of a 100 m long × 25 sq. mm cable (rated at 100 A) is to be checked. Which of the following results would you anticipate?
Between 0,1 Micro Ohm and 1,0 Micro Ohm.
Between 0,1 and 1,0 M Ohm.
When starting three phase induction motors which of the following starting methods will immediately apply rated voltage to the machine?
Continuity testing of a delta connected three phase induction motor yields the following results; U-V = 3 Ohms, V-W = 3 Ohms, W-U = 6 Ohms. Which of the following is the likely condition?
Short circuit between V and Earth.
Partial fault between W and U.
Open circuit winding between W and U.
Short circuit winding between W and U.
What is the advantage of a transmitter with a narrow measurement range?
Better linearity and increased accuracy.
Do not need any calibration.
How can a lead-acid type battery be checked to confirm if it is fully charged or not?
Measure the relative density (specific gravity) of the electrolyte.
Measure the temperature of the electrolyte.
Measure the battery voltage.
Measure the level of the electrolyte.
When polarity of the incoming power line is reversed, what happens to the DC motor?
Motor still rotates in the same direction.
Motor rotates in the reverse direction.
This circuit consists of a voltage source V, a change-over switch S, a resistor R and a capacitor C. The voltage/time figures 1 to 4 show changes in the voltage V(C) when the switch S is suddenly shifted from position 1 to 2 at time t = 0. Only one of the diagrams is correct. Which?
This figure shows a transformer, with two windings, N(1) = 2 000 and N(2) = 1 000 turns, on a common magnetic circuit. Assume that there is no energy loss in the transformer itself. Calculate the current l(2) when the current l(1) = 2 A.
What should be the healthy continuity resistance of a 220 V, 2,2 kW, 10 A heating element, when checked near to it’s rated operating temperature?
Which electronic component or system is this graphical symbol illustrating?
Transformer with ferromagnetic core.
3-phase sine-wave generator.
Can a ZENER BARRIER be installed in a hazardous area?
Only if properly marked for such installation.
Only in equipment operating on very low voltage.
Yes, that’s what the zener barrier is made for.
No, as only the output from the barrier is intrinsically safe this is not allowed.
When there is a need to interrupt current flow in a high voltage system it may be very difficult to quench the electrical arc which is generated at the circuit breaker contacts. Which of the following arcing media is commonly found in high voltage marine switchgear?
The circuit shows a full-wave bridge rectifier. Which electronic component should be connected between “a” and “b” in order to obtain reduced ripple voltage to the load RL.