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Electricity Questions and Answers for Viva

Frequently asked questions and answers of Electricity in Current Electricity of Electrical Engineering to enhance your skills, knowledge on the selected topic. We have compiled the best Electricity Interview question and answer, trivia quiz, mcq questions, viva question, quizzes to prepare. Download Electricity FAQs in PDF form online for academic course, jobs preparations and for certification exams .

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Interview Question and Answer of Electricity


Question-1. How is energy transferred by electrical working?

Answer-1: It flows in an electrical circuit



Question-2. What is electrical current?

Answer-2: The rate of flow of electrical charge



Question-3. In most circuits, what is the charge that flows to carry the current?

Answer-3: Electrons



Question-4. What is needed for electrical charge to flow through a closed circuit?

Answer-4: A source of potential difference.



Question-5. What is a circuit diagram?

Answer-5: Simplified circuit drawings using symbols



Question-6. What is a series circuit?

Answer-6: A circuit where all of the components are connected in one loop.



Question-7. What is the parallel circuit?

Answer-7: A circuit where there is more than one loop of components.



Question-8. What can you say about the current anywhere in a series circuit?

Answer-8: It stays the same



Question-9. What happens to the current in a parallel circuit?

Answer-9: It is shared between the branches but the total stays the same



Question-10. What happens if there is a break in a series circuit?

Answer-10: The current stops flowing



Question-11. What happens if there is a break in one branch of a parallel circuit?

Answer-11: The current stops in that branch only



Question-12. What is the word equation for flow of charge?

Answer-12: charge flow = current x time



Question-13. What is the symbol equation for flow of charge?

Answer-13: Q = I t



Question-14. What is the unit and unit symbol of charge?

Answer-14: Coulombs, C



Question-15. What is the unit and unit symbol of current?

Answer-15: Amps, A



Question-16. What piece of equipment is used to measure current?

Answer-16: Ammeter



Question-17. How are ammeters arranged in a circuit?

Answer-17: In series



Question-18. What is the direction of conventional current?

Answer-18: Positive to negative



Question-19. What is another name for potential difference?

Answer-19: Voltage



Question-20. What is potential difference?

Answer-20: The amount of energy lost or gained by one unit of charge



Question-21. What is the unit and unit symbol of potential difference?

Answer-21: Volts, V



Question-22. What piece of equipment is used to measure potential difference?

Answer-22: Voltmeter



Question-23. How are voltmeters arranged in a circuit to measure the potential difference?

Answer-23: In parallel to the component you are measuring



Question-24. What happens to the potential difference in series circuit?

Answer-24: It is shared between the components



Question-25. What should all of the potential differences add up to in a series circuit?

Answer-25: The potential difference of the battery



Question-26. What happens to the potential difference in a parallel circuit?

Answer-26: The total potential difference across each branch is the same as the potential difference from the battery



Question-27. What equation links potential difference, current & resistance?

Answer-27: Potential difference = Current x Resistance



Question-28. What is the symbol equation for potential difference?

Answer-28: V = I R



Question-29. What is resistance?

Answer-29: Anything in a circuit that slows down the flow of current



Question-30. What is the unit and unit symbol of resistance?

Answer-30: Ohms, Ω (omega)



Question-31. What do we call materials with a low resistance?

Answer-31: Conductors



Question-32. What do we call materials with a high resistance?

Answer-32: Insulators



Question-33. What is the job of a battery in a circuit?

Answer-33: Is the source of the potential difference (Provides the energy)



Question-34. What happens if you add more batteries to a circuit?

Answer-34: More current will flow, the current will increase



Question-35. What happens to the resistance if you add more resistors in series?

Answer-35: it increases



Question-36. What happens to the resistance if you add more resistors to each branch in parallel?

Answer-36: Total resistance decreases



Question-37. In the required practical on measuring resistance, what is the dependent variable?

Answer-37: Resistance



Question-38. For some resistors, the resistance always remains constant. In others, it can change as?

Answer-38: The current changes.



Question-39. At a constant temperature, the current through an ohmic conductor is?

Answer-39: Directly proportional to the potential difference across the resistor.



Question-40. What does it mean that a component is "ohmic"?

Answer-40: Resistance remains constant as current changes.



Question-41. What happens to the resistance of a filament lamp as the potential across the lamp increases?

Answer-41: It increases.



Question-42. Why does the resistance of a filament lamp increase as the potential difference across it increases?

Answer-42: The wire heats up so particles move faster, getting in the way of moving charges more often.



Question-43. Describe the current flow through a diode?

Answer-43: It can only flow in one direction. There is a very high resistance in the reverse direction.



Question-44. Why does a diode only allow current to flow in one direction?

Answer-44: The particles act like a valve, only allowing charges to travel in one direction.



Question-45. What is a thermistor?

Answer-45: A temperature dependent resistor.



Question-46. What happens to the resistance of a thermistor when the temperature increases?

Answer-46: It decreases



Question-47. Why does resistance of a thermistor decrease when the temperature increases?

Answer-47: Thermal energy helps the particles to line up and allow charges through more easily.



Question-48. When would a thermistor be useful?

Answer-48: Thermostats ? to make things change with temperature.



Question-49. What is an LDR?

Answer-49: A Light Dependent Resistor



Question-50. What happens to the resistance of an LDR when the light intensity increases?

Answer-50: It decreases.



Question-51. Why does resistance of an LDR decrease when the light intensity increases?

Answer-51: Light energy helps the particles to line up and allow charges through more easily.



Question-52. When would an LDR be useful?

Answer-52: Light sensors - to switch on lights when it gets dark.



Question-53. To measure the resistance of a component, what measurements should be made?

Answer-53: Measurements of the current through the component and the potential difference across it.



Question-54. In the required practical on investigating I-V characteristics of components, what is the independen

Answer-54: The current through the component



Question-55. What happens to the potential difference across a wire when the length of the wire increases?

Answer-55: The longer the wire, the higher the resistance



Question-56. In a series circuit, what can be said about the current?

Answer-56: The current is the same through each component.



Question-57. In a series circuit, what can be said about the potential difference?

Answer-57: The sum of the potential difference across each component is equal to the potential difference of the battery



Question-58. In a series circuit, what can be said about the resistance?

Answer-58: The total resistance is the sum of the individual resistances.



Question-59. What is the equation for the total resistance of a series circuit?

Answer-59: Rtotal = R1 + R2 ...



Question-60. In the branches of a parallel circuit, what can be said about the current?

Answer-60: The total current is equal to the sum of the current in each branch



Question-61. In the branches of a parallel circuit, what can be said about the potential difference?

Answer-61: The potential difference across each branch is the same and the battery



Question-62. In the branches of a parallel circuit, what can be said about the resistance?

Answer-62: The total resistance in the circuit is less than the resistance of the lowest of the resistor in any branch



Question-63. Why does adding resistors in parallel decrease the total resistance?

Answer-63: There are more routes for electrons to take between the branches, so it is easier for current to flow.



Question-64. What does DC stand for?

Answer-64: Direct Current



Question-65. In what direction does DC current flow?

Answer-65: Current flows in one direction (positive to negative for conventional current)



Question-66. What type of circuits use DC?

Answer-66: Circuits powered by a cell or battery



Question-67. What does AC stand for?

Answer-67: Alternating Current



Question-68. What type of current does mains electricity use?

Answer-68: Alternating current



Question-69. What the frequency of the AC domestic electricity supply in the UK?

Answer-69: 50 Hz, (50 cycles per second)



Question-70. What is the potential difference of the domestic electricity supply in the UK?

Answer-70: 230 V



Question-71. How many wires make up the cables of most electrical appliances?

Answer-71: 3



Question-72. Why is each wire wrapped in a plastic coating?

Answer-72: As a safety feature. The plastic acts as an insulator from the electricity



Question-73. What does the colour coding on each wire identify it as?

Answer-73: Brown - live wire
Blue - neutral wire
Green and yellow stripes - earth wire



Question-74. What does the live wire do, and what is its potential?

Answer-74: It carries the alternating potential from the power supply. The potential difference between the live wire and earth is around 230 V.



Question-75. What does the neutral wire do, and what is its potential?

Answer-75: It completes the circuit, and is close to earth potential (0 V).



Question-76. What does the earth wire do, and what is its potential?

Answer-76: It is a safety wire to stop the casing of the appliance from becoming live, so is at 0V and only carries a current if there is a fault.



Question-77. When is a live wire dangerous?

Answer-77: They are always dangerous when a current is flowing, because they carry a potential of 230V.



Question-78. Why is it dangerous to touch a live wire?

Answer-78: A persons potential is 0V. Touching the live wire causes a potential difference of 230V and the charge is carried through the person.



Question-79. What is power?

Answer-79: The amount of energy transferred per second



Question-80. What is the unit of power and the unit symbol?

Answer-80: Watts, W



Question-81. What does the amount of energy an appliance transfers depend on?

Answer-81: The power of the appliance and how long it is switched on for.



Question-82. What does work have to do with electric circuits?

Answer-82: Work is done when charge flows in a circuit.



Question-83. What two word equations relate energy transferred, power, time, charge and potential difference?

Answer-83: Energy transferred = Power x Time energy transferred = Charge x Potential difference



Question-84. What two symbol equations relate energy transferred, power, time, charge and potential difference?

Answer-84: E = P t
E = Q V



Question-85. What is the unit and unit symbol of energy?

Answer-85: Joules, J



Question-86. What is the power transfer in a circuit related to?

Answer-86: The potential difference across the circuit, the current through it and the energy changes over time.



Question-87. What two word equations relate power, potential difference, current and resistance?

Answer-87: Power = potential difference x current; Power = (current)2 x resistance



Question-88. What two symbol equations relate power, potential difference, current and resistance?

Answer-88: P = V I or P = I2 R



Question-89. What does the power rating of an appliance mean?

Answer-89: The maximum operating power that is safe for the appliance.



Question-90. What is the National Grid?

Answer-90: The National Grid is a system of cables and transformers linking power stations to consumers.



Question-91. What is a transformer?

Answer-91: A device which alters the potential difference and current of electricity in the cables.



Question-92. What does a step-up transformer do?

Answer-92: They are used to increase the potential difference from the power station to the transmission cables



Question-93. Why do we increase the potential difference across the cables?

Answer-93: To decrease current and reduce the energy loss due to heating.



Question-94. What does a step-down transformer do?

Answer-94: They are used to decrease the potential difference for safe domestic use.



Question-95. Why is static-electricity called "static"?

Answer-95: It is related to "static" (or still) electrons which build up on materials.



Question-96. What type of charge do electrons have?

Answer-96: Negative charge



Question-97. How is static electricity produced?

Answer-97: When certain insulating materials are rubbed, the friction causes negatively charged electrons to move from one material to another



Question-98. Which sub-atomic particle is transferred between materials to generate a static charge?

Answer-98: Negatively charged electrons



Question-99. If a material gains electrons what charge will it have?

Answer-99: The material that gains electrons becomes negatively charged.



Question-100. If a material loses electrons what charge will it have?

Answer-100: The material that loses electrons is left with an equal positive charge.



Question-101. What happens when electrically charged objects are brought close together?

Answer-101: When two electrically charged objects are brought close together they exert a force on each other.



Question-102. What is the name of the force that exists between charged objects and what type of force is it?

Answer-102: Electrostatic, Non-contact (the objects do not need to touch)



Question-103. What happens to two objects with the same type of charge?

Answer-103: They repel each other.



Question-104. What happens to two objects with different types of charge?

Answer-104: They are attracted to each other.



Question-105. What is an electric field?

Answer-105: A field created around a sphere of charge



Question-106. What happens if another charged object is placed in the field?

Answer-106: A second charged object placed in the field experiences a force.



Question-107. Where is the charge strongest in an electric field?

Answer-107: The closer an object is to the charged sphere, the stronger the force



Question-108. In what direction do field lines flow in a positive and negative charge?

Answer-108: Out of a positive object, into a negative object



Question-109. How do field lines show the strength of a field?

Answer-109: The closer the lines the stronger the field



Question-110. When will static cause a spark?

Answer-110: If there is a high enough potential difference between a charged objecta nd the earth/earthed object (0V)



Question-111. What causes the spark?

Answer-111: An electric field occurs between the charged object and the earth object. Air particles in the electric field are ionised (electrons are removed) Ionised air is a conductor and so a current flows between the charged object and the earthed object




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