Basic Electrical Engineering MCQs with Answers 1

1. Matter can exist in any one of four states—solid, liquid, gas and: 

A.  plasma
B.  molecules
C.  air
D.  conductance


2. The smallest particle into which any one chemical can be divided without changing the characteristics of that chemical is called: 

A.  an atom
B.  a molecule
C.  a proton
D.  an electron


3. Atoms are very small particles that: 

A.  can be seen clearly by super-electron microscopes
B.  are believed to be the smallest part of matter
C.  have never been seen directly by the human eye
D.  cannot be subdivided into smaller parts


4. The nucleus of an atom contains protons, which are, 

A.  negatively charged
B.  neutrally charged
C.  alternately charged
D.  positively charged


5. In an atom, it is assumed that the attraction between the positively charged nucleus and the negatively charged electrons provides the force necessary to keep the electrons adjacent to the nucleus, while their motion keeps the electrons: 

A.  from plunging into the nucleus
B.  close to the nucleus
C.  positively charged
D.  from forming covalent bonds


6. The atomic number, of an element is the number of: 

A.  atoms in a molecule of that element
B.  protons in an atom of that element
C.  electrons in the outer orbit of atom of that element
D.  neutrons required to balance the negative protons


7. The number and arrangement of electrons around the nucleus of an atom determines: 

A.  how many molecules there will be in an atom
B.  number of molecules in a mixture
C.  many of the properties of that atom
D.  the arrangement of the crystals in a lattice


8. The outer shell of an atom is often called the: 

A.  proton shell
B.  protecting shell
C.  atomic number ring
D.  valency ring


9. A non-ionised copper atom has 29 electrons in its orbits distributed as 2, 8, 8, 10, 1. For these reasons, copper is said to be a: 

A.  good conductor
B.  poor conductor
C.  good insulator
D.  semi-conductor


10. Sulphur has an electron configuration of 2, 8, 6 with six electrons in its outer orbit, and is said to be a: 

A.  good conductor
B.  poor conductor
C.  semi-conductor
D.  electro-positively acceptor


11. The process by which an originally neutral atom becomes charged by the removal of electrons is called: 

A.  co-valent bonding
B.  neutralisation
C.  ionisation
D.  chemical bonding


12. An electric current is established when: 

A.  a material such as copper is formed into a wire
B.  the electrons from one atom and migrate to another electron
C.  free electrons drift around with no overall direction of movement
D.  electrons flow from one place to another under an external influence


13. When current flow occurs in a solid conductor, an external influence causes the electrons to be attracted: 

A.  towards the positive terminal and away from the negative terminal
B.  towards the negative terminal and away from the positive terminal
C.  from the positive terminal back to the positive terminal
D.  from the negative terminal back to the negative terminal


14. When current flow occurs in a liquid, the: 

A.  positive ions give up an excess electron at a negative electrode, and the positive ions pick up an electron at the negative electrode
B.  negative ions give up an excess electron at a positive electrode, and the positive ions pick up an electron at the negative electrode
C.  negative ions give up an excess electron at a positive electrode, and the negative ions pick up an electron at the negative electrode
D.  negative ions give up an excess electron at a positive electrode, and the positive ions pick up an electron at the positive electrode


15. Gas atoms: 

A.  are fixed in a regular arrangement characteristic of the gas
B.  will migrate towards the negative electrode, where they receive a proton
C.  are free to move around as independent molecules
D.  will lock into a regular pattern when they receive a charged electrode


16. The energy levels in a plasma are so high that the atoms are ionized and the electrons flow directly through an electric field, from: 

A.  positive to negative
B.  protons to neutrons
C.  the plasma to both electrodes
D.  negative to positive


17. Look at the following diagram:      
The ebonite rod has been rubbed with fur to give it a negative charge, while the glass rod have been rubbed with silk to also have a negative charge. When the two rods are brought near one another as shown in the drawing, there will be a: 

A.  force of attraction between the rods
B.  force of repulsion between the rods
C.  force of both attraction and repulsion between the rods
D.  neutral force between the rods


18. If an electrically charged glass rod is suspended from silk thread, a second glass rod that has been rubbed with silk will: 

A.  attract it when brought near
B.  repel it when brought near
C.  have neither attraction or repulsion when brought near
D.  will rotate anticlockwise when brought near


19. A material with an electrostatic charge is said to possess an electrical potential, and the difference in electrical potential between two bodies is measured in: 

A.  amperes
B.  ohms
C.  volts
D.  watts


20. In dry weather, a person may experience an electric spark by touching a car door. This is because the: 

A.  car tyres prevent the car from picking up an electrostatic charge
B.  person has insulated shoes
C.  person has discharged all charges to the ground
D.  car has picked up an electrostatic charge


21. An electron flow can only occur if a conducting path exists between two bodies and if there is a sufficient difference in potential between those bodies to cause an electron flow. The force that causes the electrons to flow is called: 

A.  electromotive force
B.  mechanical force
C.  magnetomotive force
D.  tangential force


22. Once the potential difference between two points has been reduced to zero, the flow of electrons will: 

A.  become unstable
B.  stop
C.  increase
D.  ionize


23. A conductor is a material that will: 

A.  prevent a current flow
B.  allow a current flow in one direction only
C.  conduct the electrical energy to where it can be used
D.  not allow unwanted flow from an electric circuit


24. The source of electricity generated by electric conductors moving through a magnetic field is called an: 

A.  electrostatic source of EMF
B.  electrolytic source of EMF
C.  electrochemical source of EMF
D.  electromagnetic source of EMF


25. A piezoelectric source of electromagnetic energy is one where the electric potential is generated by: 

A.  placing a crystal under stress
B.  dissimilar metals being exposed to heat
C.  the conversion of light into electricity by solar arrays
D.  friction between appropriate materials


26. The great bulk of electrical energy is generated through electromagnetic generation. Fossil fuel is burned to generate the heat required to: 

A.  expose dissimilar metals to large values of heat
B.  turn water into steam to drive mechanical turbines
C.  drive large solar arrays
D.  operate a hydro-electric generator


27. When driving supply system alternators, gas turbines, are noted for their good efficiency: 

A.  and a normally slow speed of rotation
B.  and slow start-up times
C.  and the ability to produce small quantities of electricity quickly
D.  but are not suitable for stand-by plants for emergencies


28. Most electrochemical sources consist of: 

A.  small electromagnetic generators
B.  large arrays of solar cells
C.  wind generators connected invertors
D.  batteries of electric cells


29. The solar cell is basically a large semiconductor diode, when light falls on the junction, light energy: 

A.  is converted directly into electrical energy
B.  will charge a bank of electrochemical cells
C.  forces the electrons in the molecules to become positive
D.  turns the turbines of a solar wind generator


30. Modern solar cells have efficiencies of around: 

A.  30%
B.  40%
C.  50%
D.  60%


31. The uses for static electricity in industry are growing. A typical use is: 

A.  low voltage supplies for crop spraying machinery
B.  high voltage transmission
C.  dust precipitation
D.  household heating appliances


32. The thermoelectric method of voltage generation is mostly used: 

A.  for large power distribution systems
B.  to measure current in high-voltage circuits
C.  to drive eco-friendly household appliances
D.  as a means of temperature measurement


33. Look at the following diagram:    
Thermocouples, as shown in the above illustration, consist of: 

A.  two dissimilar metals joined at a point where the heat is applied
B.  two dissimilar metals joined to number of thermometers
C.  metals that have a melting point of 100° Celsius
D.  metals that will melt at the rated reading temperature


34. When generating a voltage by the piezoelectric effect, the value of the voltage is: 

A.  directly proportional to the luminous flux
B.  directly proportional to the applied pressure
C.  inversely proportional to the temperature of the striker
D.  inversely proportional to the heat applied to the junction


35. The natural rate of resonance of a Piezo crystal depends mainly on the: 

A.  radio transmitter being driven
B.  ultrasonic frequency of the sound waves
C.  angle of the cut and the physical dimensions
D.  distortion voltage of the applied mechanical forces


36. Early power-distribution systems supplied consumers with: 

A.  high-voltage AC. power
B.  a 6.6 kilovolts A.C. supply for home use
C.  alternating current DC power
D.  direct-current DC power


37. Almost without exception, electrical energy is today distributed to consumers using: 

A.  a three-phase four-wire system
B.  low-voltage direct current DC system
C.  a 6.6 kilovolts A.C. supply for home use
D.  three-wire direct current DC distribution systems


38. The reason for using high voltages for the long-distance transmission of power is to: 

A.  keep the sub-station transformers operating
B.  reduce power-transmission losses
C.  increase the need for power stations
D.  ensure that the sub-stations have enough current


39. Look at the following diagram:      
The diagram shows a stylized layout for an electrical transmission and distribution system. With reference to the diagram, the item marked ‘3’ is a: 

A.  transmission line
B.  pole-top distribution transformer
C.  distribution substation
D.  distribution line


40. Materials which offer a high opposition to the flow of electricity are called: 

A.  conductors
B.  semi-conductors
C.  super conductors
D.  non-conductors or insulators


41. Metals do not conduct equally well. Of the metals, the best conductor is: 

A.  silver
B.  copper
C.  gold
D.  aluminum


42. The most outstanding characteristic of an insulator is that under normal conditions it contains: 

A.  a large number of free electrons
B.  very few or no free electrons
C.  frequent conducting elements
D.  no valence ring in the atoms


43. At very low temperatures, some materials exhibit a condition known as superconductivity. At the superconducting temperatures: 

A.  the material becomes an insulator
B.  conducts in one direction only
C.  all resistance in the conductor disappears
D.  the resistance of the conductor increases sharply


44. If the current path is not continuous between two points of potential difference, the circuit is referred to as: 

A.  a short circuit
B.  a closed circuit
C.  an outside circuit
D.  an open circuit


45. To maintain a continuous current flow in a circuit, a continuous source of electrical energy must be provided to: 

A.  maintain the potential difference at the beginning of the circuit
B.  ensure a high circuit resistance value
C.  keep the insulation at the same level as the voltage
D.  prevent the current from flowing though the electrical energy source


46. When a “short-circuit” occurs in an electrical circuit: 

A.  the energy source does not provide any current
B.  excessive current flows from the energy source
C.  some electrons in the conductor become short of energy
D.  the circuit current will be short on amperes


47. Electric current is the coordinated flow of electrons from: 

A.  a point of higher potential to a point of lower potential
B.  the circuit conductor to the circuit insulator’s neutrons
C.  a point of lower potential to a point of higher potential
D.  north pole of a magnetic source to the south pole


48. In a circuit, conventional current flow is said to go from: 

A.  negative to positive
B.  negative to negative
C.  positive to positive
D.  positive to negative


49. Electromotive force is: 

A.  the electrical pressure that causes a current to flow
B.  measured in amperes and flows through a circuit
C.  the opposition to current flow in an electrical circuit
D.  the force of motion that prevents movement of electrons


50. The rate of flow of electricity is measured in: 

A.  volts per meter
B.  coulombs per second
C.  coulombs per electron
D.  ohms per ampere


52. Ammeters are used to measure the: 

A.  potential difference between two points
B.  resistance flowing in a circuit with a battery
C.  electromotive force present in a circuit
D.  current, which flows through a circuit


53. Ammeters have very low resistance so that they will not restrict the flow of current in a circuit any more than necessary. If they are connected in parallel with a voltage source: 

A.  serious damaged could result from the high current flow
B.  the current flow will be too small to register on the scale
C.  the resistance will be too high for current to flow
D.  the voltage source will flow through the ammeter


54. Voltmeters are intended to measure voltage and therefore are connected: 

A.  in series with the voltage source
B.  in parallel with the voltage source
C.  so that the circuit current is bypassed
D.  after the circuit control switch


55. Look at the following diagram:      
To read the voltage across the load resistor in the above circuit, the voltmeter should be connected to points: 

A.  ‘A’ and ‘B’
B.  ‘B’ and ‘C’
C.  ‘C’ and ‘D’
D.  D.’A’ and ‘C’


56. The maximum capacity of a meter is termed its full-scale deflection value f.s.d. If any meter pointer moves past the full scale deflection, then the meter: 

A.  will read more accurately
B.  cannot be used on direct current circuits
C.  will need to be unwound with opposite current
D.  could be seriously damaged


57. Ohm’s Law states that the current flowing between any two points in an electric circuit is directly proportional to the: 

A.  potential difference between the two points
B.  resistance between the two points
C.  opposition to current flow in the circuit
D.  size of the conductors used for the circuit


58. Look at the following diagram:      
In the above circuit, if the lamp has a resistance of 6 W, when the switch is closed the current in the circuit will be: 

A.  72 A
B.  2 A
C.  12 A
D.  D.3 A


59. A given lamp draws 4 A when powered by a 12 V battery. The resistance of this lamp is: 

A.  48 W
B.  12 W
C.  3 W
D.  0.33 W


60. According to Ohm’s Law, the voltage between two points in a circuit is equal to the: 

A.  current divided by the resistance
B.  current divided by the voltage
C.  current multiplied by the voltage
D.  current multiplied by the resistance


61. Power is defined as the: 

A.  rate of doing work or expending energy
B.  rate of current flow in a circuit
C.  amount of voltage required to overcome the resistance
D.  amount of watts expended each day by an electrical machine


62. Power can be measured directly with an instrument known as: 

A.  an ammeter
B.  a wattmeter
C.  a voltmeter
D.  an ohmmeter


63. The power dissipated by a resistor can be determined using the formula: 

A.  P = R2/V
B.  P = V x R
C.  P = I2 x R
D.  P = V x R


64. A car with a 12 V battery has a driving light rated at 100 W each. When the light is switched on, the current drawn from the supply will be: 

A.  100 A
B.  0.12 A
C.  12.0 A
D.  8.3 A


65. A 230 V household light fitting has 6 x 40 W lamps. The value of current drawn from the supply will be: 

A.  1.04 A
B.  0.79 A
C.  2.30 A
D.  5.75 A


66. Look at the following diagram:      
With reference to the connection diagram for a wattmeter shown above, the meter has two measuring circuits; one to measure the current and the other to measure the: 

A.  circuit resistance
B.  supply voltage
C.  rate of flow of the current
D.  opposition to current flow of the meter


67. The electrical energy consumed by a circuit is a product of the 

A.  current and voltage
B.  voltage and resistance
C.  power and time
D.  power and voltage


68. An electric heater rated at 1200 W has been switched on for an average of 4 hours per day for 7 days. The electrical energy consumed during that period will be: 

A.  4.8 kWh
B.  28.0 kWh
C.  8.4 kWh
D.  33.6 kWh


69. Look at the following diagram:
In a given time period a private residence consumes 1200 kWh of energy charged at the domestic rate and 750 kWh of energy charged at the off-peak 1 rate. Using the above tariffs, the cost of the electric energy for the period will be: 

A.  $161.15
B.  $150.90
C.  $123.00
D.  $27.90


70. Resistors are components that resist the flow of: 

A.  voltage in a circuit
B.  electric current around a circuit
C.  power through an appliance
D.  electromotive force in a conductor


71. In electronics and some electrical applications, resistors are used to control: 

A.  voltage flow
B.  resistance flow
C.  current flow
D.  electric tariff flow


72. An ‘inductor’ is a component that can induce: 

A.  an electrostatic field the space between two plates
B.  a voltage to flow around a conductor
C.  a resistor to become incandescent
D.  an electromagnetic field in the space around a conductor


73. When current flows through an inductor, a magnetic field is generated which then passes through other parts of the coil. This causes a voltage to be generated in the coil that: 

A.  opposes the original current flow
B.  is parallel to the original magnetic field
C.  assists the original current flow
D.  will be equal to 100 v a.c.


74. A transformer can transform voltages from one value to another. It does this by converting electrical energy to: 

A.  mechanical energy
B.  magnetic energy
C.  electrostatic energy
D.  heat energy


75. Capacitors are devices for storing an electrical charge in: 

A.  a magnetic field
B.  amperes per watt
C.  an electrostatic field
D.  an uninsulated container


76. Chimney stacks in power stations often have electrostatic generators that energise the smoke particles so they: 

A.  have no electrostatic charge
B.  go into the atmosphere more easily
C.  will be carried away from the chimney top by the wind
D.  become attached to an electrostatic grid


77. One example of the electrochemical effect of an electric current is: 

A.  the industrial process of electroplating
B.  an electro-magnetic hoist in a scrap steel yard
C.  an electric motor
D.  a heating element for an electric water-heater


78. When a current flows through a conductor heat is produced, which: 

A.  stabilizes the conductor at ambient temperature
B.  raises the temperature of the conductor
C.  lowers the temperature of the conductor
D.  has no effect on the temperature of the conductor


79. The magnetic effect of an electric current can be increased by: 

A.  lowering the value of electric current
B.  ensuring the resistance of the circuit is adequate
C.  creating coils of conductors called solenoids
D.  moving winding coils further apart


80. The general effect of electric shock on the human body is such that levels of current less than 10 mA cause muscle pain and shaking, while levels up to about 30 mA: 

A.  will have no effect
B.  usually cannot be felt
C.  will generally not cause any pain
D.  can cause severe muscle contractions


81. Heat is energy stored in a body, whereas temperature is: 

A.  the potential of that heat
B.  the amount of electrons in the heat
C.  measured in joules
D.  a measure of the electrical energy in a body


82. When heat is stored in a body, the temperature rises according to the: 

A.  value of resistance of that body
B.  specific heat capacity of that body
C.  amount of specific temperature coefficient
D.  ambient association of the energy levels present


83. The SI unit of temperature is the: 

A.  degrees Celsius
B.  degrees Centigrade
C.  Kelvin
D.  Thompson


84. Absolute zero temperature is considered to be: 

A.  273.16º K
B.  –273.16 K
C.  273.16º C
D.  –273.16º C


85. The SI unit for heat energy is the: 

A.  joule
B.  degree
C.  kilogram-metre
D.  ampere


86. The amount of energy that is contained in a body of material has been found to depend on three parameters. These are: the mass of material in the body, the type of material and the: 

A.  specific heat capacity of the material
B.  temperature of the material
C.  electrostatic condition of the material
D.  increments between the degrees of heat


87. The specific heat capacity of a material is defined as the quantity of heat energy required to raise the temperature of a mass of: 

A.  one kilogram by two degrees Celsius
B.  two kilograms by one Kelvin
C.  one kilogram by one Kelvin
D.  one kilogram by one degree Fahrenheit


88. An urn containing 15 litres of water is heated from room temperature 25ºC to boiling point 100ºC (Note: The specific heat capacity of water is 4180 J/kgK). The amount of heat energy delivered to the urn is: 

A.  1.125 MJ
B.  1.5675 MJ
C.  4.180 MJ
D.  4.7025 MJ


89. A aluminium block of mass 1.25 kg has 2.2 kJ of heat energy added (Note: The specific heat capacity of copper is 390 J/kgK). If the initial temperature was 20ºC, then the final temperature of the block will be: 

A.  24.5°C
B.  25.4°C
C.  45.2°C
D.  42.5°C


90. There are three recognised processes of heat transfer—conduction, convection and: 

A.  radio isolation
B.  radiation
C.  electrostatic
D.  magnetic


91. The rate of heat conduction through a material depends on the temperature difference across the material, the cross-sectional area of transfer path, the length of transfer path and the: 

A.  age of the material
B.  insulation resistance of the material
C.  type of material
D.  voltage applied to the material


92. Poor thermal conductors of heat offer higher opposition to heat energy flow and are therefore considered to be: 

A.  electrical insulators
B.  semi-conductors
C.  joule equivalent materials
D.  thermal insulators


93. The thermal conductivity of a material is the ability of that material to: 

A.  transmit heat by conduction
B.  transmit incandescence
C.  conduct an electric current through a thermal barrier
D.  thermally conduct an electric current via an insulator


94. The heat energy that results from an electric current flow is determined by, the power used by the appliance multiplied by the: 

A.  current in the circuit
B.  length of time it is used for
C.  thermal resistance of current flow
D.  voltage applied to the circuit


95. The heat energy generated by an electric current can be determined using the formula: 

A.  H = IR2t
B.  H = IRt2
C.  H = I2Rt
D.  H = I2R2t


96. An electric motor has been overloaded and is stalled. The supply is 32 volts and the motor has a winding resistance of 4 W. If it takes 1.25 minutes for the protection to operate, then the heat energy generated will be: 

A.  2.4 kJ
B.  3.2 kJ
C.  12.8 kJ
D.  19.2 kJ