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Heim Online-Tests CBT Alle Arten von Schiffen Ch-Eng / 2nd-Eng Test for seamans about Electric Propulsion, Fundamentals (CBT)
Online-Test: Test for seamans about Electric Propulsion, Fundamentals (CBT)
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A single phase AC generator produces a 50 Hz output. How long does it take for one complete cycle of the voltage?
20 milliseconds.
50 milliseconds.
100 milliseconds.
1 second.
An electrical network consists of 3 loads with different power factors. Which of the following best describes how the overall network power factor can be calculated?
The three powers would need to be added together using vector addition.
The three powers would need to be added together using simple addition.
The apparent powers of all 3 loads can be added together and divided by the total power.
The arithmetic mean of the three power factors can be used.
Here are the terminal connections on an electric induction motor. Which of the following best describes the arrangement?
3 phase – Star connected.
3 phase – Star connected with insulated neutral.
3 phase – Delta connected.
3 phase – Star connected with earthed neutral.
Here are the terminal connections on an electrical machine. Which of the following best describes the arrangement?
3 phase – Star connected with neutral.
3 phase – Star connected.
3 phase – Delta connected with neutral.
3 phase – Delta connected with split winding.
In relation to an electrical motor: which of the following best describes what “star point” is?
It is the point where the end of one winding is connected to the start of the next.
It is the point at which one of the ends of all 3 windings are shorted together.
It is a point provided for test equipment.
It is the point at which the motor is unable to turn.
In relation to electrical systems: which of the following best describes what the definition of “power” is?
Power is the rate of energy conversion.
Power is the amount of energy converted.
Power is the amount of electricity available at any point in the system.
Power is the rate of generator fuel being burnt.
Study of an electrical circuit results in the calculation of current phasors for resistive, inductive and capacitive components of the total current as shown. If the circuit voltage is 200 V what will be the value of reactive power (Q)?
Q = 2 000 VAr.
Q = 5 000 VAr.
Q = 8 000 VAr.
Q = 12 000 VAr.
The power factor of a large electric motor changes from 0,8 to 0,7 while its kW load remains constant. Which of the following best describes the effect of this on the electrical network?
The network power factor will be automatically increased to compensate for the change.
The network will not be affected as the active power has not changed.
The current taken from the network will decrease.
The current taken from the network will increase.
What is the minimum number of stator coils required to make a 3 phase electrical generator?
1.
4.
3.
2.
When a conductor is moved through a magnetic field an EMF is produced. Which one of the following is a way to increase the value of EMF produced?
Move the conductor more quickly.
Move the conductor in circles.
Change the conductor for one with a lower resistance.
Change the conductor for one with a higher resistance.
When considering an electromagnet which one of the following factors effects its relative permeability?
The current applied.
The material of the core.
The voltage applied.
The diameter of the coil.
When considering electrical systems: which of the following best describes why we may use “Fleming’s left hand rule”?
To determine the relative directions of motion, current and field in a motor.
To determine the best way to twist conductors in a multicore cable.
To determine the phase angle of the load.
To count the number of vibrations per cycle in a machine.
When used to construct a “power triangle” for an electrical circuit which of the following best describes what is represented by a phasor’s direction?
Its phase position with respect to some reference, usually the system voltage.
The value of the quantity being represented.
The angle of the generator rotor with respect to a reference point.
Whether the quantity being measured is active or reactive.
Which of the following best describes one of the major advantages of using 3 phase electricity on a ship rather than single phase?
Reduced cable costs.
Reduced number of conductors.
Reduced number of transformers.
Reduced maintenance.
Which of the following best describes one of the major problems with using only single phase electricity for a ship’s electrical system?
Single phase machines require higher maintenance.
Single phase networks require more conductors.
The torque variations cause excessive torsional vibrations in single phase machines.
Single phase networks require fewer conductors with larger diameters.
Which of the following best describes the construction of a simple electrical capacitor?
Two conducting plates separated by a gap of a dielectric substance.
Two conducting plates separated by a semiconductor.
Two insulating plates separated by a conducting substance.
Loops of conductor separated by an insulating substance.
Which of the following best describes the relationship between the current and voltage in a circuit with pure capacitance which is supplied with single phase AC?
The peak current will lag that of the voltage by 90°.
The current and voltage will reach their maximum at the same time.
The peak current will lead that of the voltage by 90°.
The voltage cycle does not affect the times at which the current reaches its maximum.
Which of the following best describes the relationship between the current and voltage in a circuit with pure inductance which is supplied with single phase AC?
The current will reach its maximum 90° after the voltage reaches its maximum.
The current will reach its maximum 90° before the voltage reaches its maximum.
The current and voltage will reach their maximum at the same time.
The voltage cycle does not affect the times at which the current reaches its maximum.
Which of the following best describes what will happen in this inductive electrical circuit when the switch is closed?
A current will flow, rising quickly before levelling off.
A current will flow, rising instantly then remain at a steady value.
A current will flow, rising quickly until the supply is switched off or reserved.
No current will flow.
Which of the following best describes what will happen to the current in this capacitive electrical circuit when the switch is closed?
A current will flow anticlockwise but will fall to zero after a time.
A current will flow anticlockwise.
A current will flow clockwise but will fall to zero after a time.
No current will flow.
Which of the following correctly describes what is happening at the instant represented by this phasor diagram?
The value of current is zero.
The value of current is falling.
The current leads the voltage.
The value of voltage is falling.
Which of the following is the best description of a “current” in an electrical circuit?
A flow of electrons.
A flow of protons.
A flow of neutrons.
The energy that produces a voltage.
Which of the following are the units used when measuring capacitance in an electrical component?
Farads.
Coulombs.
Teslas.
Teslas per m2.
Which of the following best describes why it is preferable to use electromagnets when constructing an electrical generator, rather than permanent magnets?
The electromagnets are bigger and therefore more robust.
The electromagnets are easier to shape.
We can control the amount of flux that electromagnets produce.
We need conductors around the magnets to carry the generator output.
Which of the following best describes why physical forces can be created from the interaction of 2 magnets?
The magnets move to make the lines of magnetic flux as short as possible.
The magnets move because of an electrical charge stored within them.
The magnets move to even out the flux density.
The magnets move if the lines of magnetic flux are forced to cross.
Which of the following can be assumed to have an unchanging value in an electrical circuit, whether it is an AC or DC circuit?
Inductance.
Resistance.
Capacitance.
Impedance.
Which of the following describes a way of increasing the Capacitance value of a capacitor?
Increase the area of the conducting plates.
Reduce the area of the conducting plates.
Increase the voltage applied to the conducting plates.
Reduce the voltage applied to the conducting plates.
Which of the following describes how the inductance of an electrical coil can be increased?
Use smaller diameter conductor.
Wind the conductor around a long plastic core.
Wind the conductor around a core that can be magnetised.
Increase the voltage applied to the inductor.
Which of the following describes the way of calculating the amount of electrical energy that can be stored in a capacitor?
Energy stored is = 1/2 CV2Watts.
Energy stored is = 1/2 CV2Joules.
Energy stored is = 1/2 LI2Joules.
Energy stored is = 1/2 LI2Watts.
Which of the following is an example of an electrical load with a power factor of approximately one?
A galley hotplate.
An induction motor while starting.
An induction motor while running.
A fluorescent light.
Which of the following is the name given to the quantity used to combine the effects of resistance, capacitance and inductance when calculating currents in an electrical circuit?
Dielectric.
Impedance.
Reluctance.
Insulation.
Which of the following would increase the capacitive reactance, X, of an electrical circuit containing a single capacitor?
A decrease in supply frequency.
An increase in the capacitor’s capacitance.
An increase in circuit voltage.
An increase in circuit current.
Which of the following would increase the inductive reactance, X, of an electrical circuit containing a single coil?
A decrease in the coil’s inductance.
An increase in supply frequency.
An increase in circuit voltage.
An increase in circuit current.
With reference to an AC electrical circuit: which of the following best describes the meaning of “in phase”?
The voltage and current rise and fall together.
The voltage starts to rise as the current starts to fall.
The voltage and current have the same value.
The circuit contains a resistor in series with an inductor.
With regard to a delta connected electrical machine: which one of the following statements is true?
The line voltage is the same as the phase voltage.
The line current is the same as the phase current.
The line voltage is larger than the phase voltage.
The line current is smaller than the phase current.
With regard to a star connected electrical machine: which one of the following statements is true?
The phase voltage is the same as the line voltage.
The phase current is smaller than the line current.
The phase current is the same as the line current.
The phase voltage is larger the line voltage.
Тест проверяет знания об основах электрической пропульсии, включая её компоненты, управление и обслуживание.
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