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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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