Test for seamans about High Voltage, Fundamentals
Test results
Your result: 93%
Right answers:
1
A 440 Volt AC source supplies 2 loads in parallel. The left load has an impedance of 44 Ohms and the right of 11 Ohms. Which of the following is the current taken from the AC supply?
Your answer is correct:
50 Amps.2
A man accidently receives an electric shock resulting in a current of 2 mA flowing through his hands and chest. Which of the following best describes the likely effect on him?
Your answer is correct:
He will feel tingling or mild pain.3
An AC circuit delivers an active power of 30 kW when supplied at 400 Volts and 125 Amps. Which of the following is the reactive power?
Your answer is correct:
40 kVAr.4
An AC electrical circuit operates at 110 Volts. Which one of the following is the circuit’s voltage rating according to this module?
Your answer is correct:
Low Voltage.5
An overcurrent relay is usually used to open a circuit breaker. Which one of the following is another function it may be used for?
Your answer is correct:
To sound an alarm.6
How do electrical engineers refer to a flow of electricity around a circuit?
Your answer is correct:
It is referred to as a current, represented by I.7
In analyzing AC electrical circuits, it is common practice to use impedances. Which one of the following best describes what an “impedance” is?
Your answer is correct:
It expresses the practical effect of resistance, capacitance and inductance for a single or group of components.8
PVC insulated cable is very popular ashore. Which one of the following best describes the reason why it is less frequently used on ships?
Your answer is correct:
It gives off poisonous halogen gas if on fire.9
Sometimes conductors are separated to prevent short circuits, using the insulating effect of the air to contain the electricity. Which 2 of the following are reasons why the gap between conductors may be larger than the minimum necessary for the rated voltage?
Correct answer:
To allow space for tools to be used.; Where there is a higher than usual risk of short circuit.Your Answer:
To allow space for tools to be used.; A sudden increase in voltage is possible.10
Sometimes it is possible to see electrical conductors, such as busbars, which have no insulation covering parts of them. Which one of the following best describes why these uninsulated live parts do not normally cause a short circuit?
Your answer is correct:
The surrounding air has been used as the insulation.11
The basic strategy to stay alive while working with high voltage systems may be summarized as DIE. What does DIE stand for?
Your answer is correct:
Disconnect, Isolate, Earth.12
The battery in the circuit shown has an output of 1,5 Volts. The resistors are 32,75 Ohms each. What voltage is dropped across the right hand resistor?
Correct answer:
1,5 Volts.Your Answer:
0,75 Volts.13
The battery in the circuit shown has an output of 12 Volts. If the resistance of the resistor is 3 Ohms what current should be flowing in the circuit?
Your answer is correct:
4 Amps.14
The battery in the circuit shown has an output of 12 Volts. If the resistance of the upper resistor is 3 Ohms what current should be flowing in the circuit?
Your answer is correct:
It cannot be calculated from the information given.15
The battery in the circuit shown has an output of 12 Volts. The resistors are 3 Ohms each. What current should be flowing through the battery connections?
Your answer is correct:
12 Amps.16
The battery in the circuit shown has an output of 24 Volts. If the resistance of the upper resistor is 3 Ohms and the lower resistor is 5 Ohms what current should be flowing in the circuit?
Your answer is correct:
3 Amps.17
The battery in the circuit shown has an output of 6 Volts. If the resistance of the resistor is 0,5 Ohms what current should be flowing?
Your answer is correct:
12 Amps.18
The battery in the circuit shown has an output of 6 Volts. If the resistance of the upper resistor is 3 Ohms and the current flowing in the circuit is 1 Amp, then what voltage is dropped across the upper resistor according to Kirchhoff’s Law?
Your answer is correct:
3 Volts.19
The battery in the circuit shown has an output of 6 Volts. The resistance of the upper resistor is 3 Ohms and the lower resistor is 9 Ohms. What voltage is dropped across the upper resistor according to Kirchhoff’s Voltage Law?
Your answer is correct:
1,5 Volts.20
The battery in the circuit shown has an output of 6 Volts. The voltage dropped across the upper resistor is 2 Volts. What voltage is dropped across the lower resistor according to Kirchhoff’s Law?
Your answer is correct:
4 Volts.21
Thermosetting insulation has been used on the cases of 2 circuit breakers, one rated for low voltage and the other for high voltage. Which of the following options best describes the difference that can be seen in the insulation?
Your answer is correct:
The insulation will be thicker on the high voltage breaker.22
Two electrical conductors are circular in cross section and are otherwise the same except that conductor 1 has twice the diameter of conductor 2. If the resistance of conductor 1 is 2 Ohms what is the resistance of conductor 2?
Your answer is correct:
8 Ohms.23
Two electrical conductors are the same except that conductor 1 is four times as long as conductor 2. If the resistance of conductor 1 is 2 Ohms what is the resistance of conductor 2?
Your answer is correct:
0,5 Ohms.24
Two identical coils are connected in separate electrical circuits. One coil is supplied by a 12 Volt DC source and the other by a 12 Volt AC source. Which one of the following describes which circuit will have the higher current flowing and why?
Your answer is correct:
The DC circuit – because the inductance does not restrict current flow.25
When calculating the resistance of an electrical conductor which one of the following is the symbol used to denote the resistivity of the conductor material?
Your answer is correct:
The symbol ρ.26
Which of the following allows the heat being produced in a conductor carrying a current to be calculated?
Your answer is correct:
I2×R.27
Which of the following best describes how a capacitor works?
Your answer is correct:
It stores energy like a fast charging battery.28
Which of the following best describes how the apparent power of an AC electrical circuit with a single coil as a load can be calculated?
Your answer is correct:
P = V×I.29
Which of the following best describes one of the ways that might cause an electrical conductor to suffer voltage overload?
Your answer is correct:
Accidental connection to the wrong supply.30
Which of the following best describes one reason why people receiving electric shocks from high voltage (HV) systems are more likely to die than those receiving shocks from low voltage (LV) systems?
Your answer is correct:
The safe exposure time to current falls rapidly as the voltage increases.31
Which of the following best describes the effect of over voltage when applied to an electrical conductor?
Your answer is correct:
It will cause insulation breakdown.32
Which of the following best describes the meaning of the symbol Ω when found in an electrical calculation?
Your answer is correct:
The quantity is expressed in Ohms.33
Which of the following best describes the reason why designers of electrical systems sometimes specify cables with a greater current carrying capacity than the current predicted to flow in service?
Your answer is correct:
The cables are to be installed in a large bundle on the boiler.34
Which of the following best describes what we mean by “power factor” in an AC electrical system?
Your answer is correct:
It is the proportion of apparent power which is delivered as active power.35
Which of the following best describes why traditionally ships’ electrical systems have operated with an insulated neutral?
Your answer is correct:
So as to minimise the risk of essential equipment tripping.36
Which of the following is the level at which electricity becomes high voltage, according to the International Electro-Technical Commission standard for ships?
Your answer is correct:
AC electricity above 1 000 Volts.37
Which of the following options best explains how we ensure that electricity flows from the power supply to the load without it “leaking” away?
Your answer is correct:
The conductor is surrounded by insulation to prevent leakage.38
Which one of the following best describes reactive power in an AC electrical circuit?
Your answer is correct:
Reactive power is easily converted back to electricity.39
Which one of the following best describes the meaning of “voltage stress” when applied to ship’s electrical cables?
Your answer is correct:
It is the voltage per millimetre of insulation.40
Which one of the following best describes the primary method of protecting against overloading of an electrical conductor?
Your answer is correct:
The conductors must be adequately rated for maximum load current under the worst environmental conditions expected.41
Which one of the following best describes what the difference is between the thermosetting and the thermoplastic insulations used on ship’s electrical equipment?
Your answer is correct:
Thermoplastic insulations soften as they get warmer and thermosetting insulations do not.42
Which one of the following best describes why a length of 10 Amp cable bought from a shop ashore may not be suitable for a circuit carrying 10 Amps on a ship?
Your answer is correct:
Temperatures on ships are often higher than ashore so that the conductor may not be cooled as effectively as assumed by the seller.43
Which one of the following best describes why arc and blast are more of a problem with high voltage (HV) electrical systems?
Your answer is correct:
The amount of energy available in a HV circuit tends to be much higher.44
Which one of the following best describes why most circuits on ships are supplied by AC electricity rather than DC?
Your answer is correct:
The voltage level of AC is easily changed.45
Which one of the following describes the best way of protecting the conductors deep inside electrical machines from the effects of excessive temperature?
Your answer is correct:
Thermistors can be built into them to sense the temperature.46
Which one of the following describes the best way to protect an electrical cable from mechanical damage where it passes through an area on deck where cargo is loaded and unloaded?
Your answer is correct:
Run the cable through steel conduit.47
Which one of the following formulas agrees with Ohms Law?
Your answer is correct:
R = V/I.48
Which one of the following is the most common reason for a rapid rise in the current flowing through an electrical circuit, to a level many times its rated value?
Your answer is correct:
A short circuit.49
Which one of the following options best describes a possible cause for the softening and weakening of the insulation around an electrical cable?
Your answer is correct:
Unexpectedly high ambient temperature.50
Which one of the following options best describes a possible reason for someone being seriously hurt following an electric shock of 10 mA, even though the current passed through the body for only a fraction of a second?
Your answer is correct:
They were thrown backwards and fractured their head.51
Which one of the following options best describes a significant problem with thermosetting types of insulation on ships?
Your answer is correct:
Thermosetting insulation is not flexible and can become damaged by impacts.52
Which one of the following options best describes the effect on an electrical cable on a ship if the cable is hit by a lightning strike?
Your answer is correct:
A voltage overload and damage to cable insulation.53
Which one of the following options best describes what happens when a charged capacitor is connected to a load in an electrical circuit?
Your answer is correct:
A DC current will flow in the opposite direction to the one that charged it.54
Which one of the following options best describes why connecting cables are usually fitted with flexible insulation?
Your answer is correct:
Flexible insulation is necessary so connections can be made.55
Which one of the following options is the way we refer to the restriction to current flow through an inductor in an AC electrical circuit? Refer to the blackboard on the right side of the screen:
Correct answer:
4.Your Answer:
1.56