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Uss module 4 chpt 5 Sources of Electricity

Uss module 4 chpt 5 Sources of Electricity

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Uss module 4 chpt 5 Sources of Electricity

  1. 1. Module 4: Gadgets Work Wonders (II) Chapter 5 Sources Of Electricity 1© Copyright Star Publishing Pte Ltd
  2. 2. Chapter 5 Sources Of Electricity 5.1 How is electricity generated and transmitted? 5.2 What are transformers used for? 5.3 Why are batteries an important source of energy? 2© Copyright Star Publishing Pte Ltd
  3. 3. Objectives  Outline the processes that produce electricity from fossil fuels to transmitting electricity to the homes and consume electricity in common household electrical appliances (in terms of conversions of energy)  Understand that electricity is transmitted from a power station through a grid of high voltage transmission lines 3© Copyright Star Publishing Pte Ltd
  4. 4. Power Stations  Power stations are building complexes where electricity is generated. They are usually described by the energy source they use. © Copyright Star Publishing Pte Ltd 4 different types of power stations run on different energy sources
  5. 5. Fossil-fuel power stations  Together, gas-fired, oil-fired and coal-fired power stations are known as fossil-fuel power stations. This is because their sources of energy (natural gas, oil and coal) are all fossil fuels. © Copyright Star Publishing Pte Ltd 5 a gas-fired power station
  6. 6. Fossil-fuel power stations  In fossil-fuel power stations, the fuels are burnt to produce heat. This burning process will produce air pollutants. Of the three types of fossil fuels, natural gas is the cleanest while coal produces the largest amount of pollutants. © Copyright Star Publishing Pte Ltd 6 an oil-fired power station a coal-fired power station
  7. 7. Power stations in Singapore  Presently, the power stations in Singapore are either oil-fired or gas-fired.  The power stations play an important role of supplying electrical energy for daily uses and to sustain our economy. © Copyright Star Publishing Pte Ltd 7 Singapore’s existing and planned power stations
  8. 8. Nuclear power stations  Nuclear power stations use energy provided by nuclear fuels to generate electricity.  They produce very little pollutants but exposure to nuclear fuels can cause nuclear burns, cancer and deformed offsprings.  Great care must be taken to prevent nuclear sources from leaking out.  However, accidents and natural disasters can break down the protection structures and cause nuclear leakage. © Copyright Star Publishing Pte Ltd 8 a nuclear power station
  9. 9. Generator in a power station  In both fossil-fuel power stations and nuclear power stations, the central piece of equipment is the generator. When the generator is turned, electricity will be produced. © Copyright Star Publishing Pte Ltd 9 generator in a fossil-fuel fired power station Activity Book Link Activity 5.1 Singapore Electricity Market Structure
  10. 10. Energy conversions in a fossil-fuel power station © Copyright Star Publishing Pte Ltd 10
  11. 11. A coal-fired power station © Copyright Star Publishing Pte Ltd 11 Activity Book Link Activity 5.2 Generating Electricity
  12. 12. Transmission of Electricity  After electricity is generated, it is transmitted from the power stations to homes and offices using long cables through an electricity grid. An electricity grid is a network of electrical cables and electrical substations.  In Singapore, most transmission cables are underground. © Copyright Star Publishing Pte Ltd 12 overhead transmission cables
  13. 13. Transmission of Electricity  To reduce energy lost during transmission, electricity is stepped up to a high voltage before transmission.  At substations near offices and homes, voltage will be stepped down to around 230 V. Stepping up and down of voltages are done using transformers. © Copyright Star Publishing Pte Ltd 13
  14. 14. Using Electrical Appliances  When we use the electrical appliances at home, the electrical energy is converted to other forms of energy. © Copyright Star Publishing Pte Ltd 14 a bulb converts electrical energy to light and heat energy
  15. 15. Using Electrical Appliances © Copyright Star Publishing Pte Ltd 15 a kettle converts electrical energy to heat energy a television converts electrical energy to light and sound energy a washing machine converts electrical energy to mechanical energy during charging of battery, electrical energy is converted to chemical potential energy stored in the battery
  16. 16. Chapter 5 Sources Of Electricity 5.1 How is electricity generated and transmitted? 5.2 What are transformers used for? 5.3 Why are batteries an important source of energy? 16© Copyright Star Publishing Pte Ltd
  17. 17. Objectives  Describe a transformer as two coils of wire wound onto a core of iron  Understand the use of step-up and step-down transformers and give examples of their use (including high voltage transmission of electricity) 17© Copyright Star Publishing Pte Ltd
  18. 18. Transformers  The label found at the back of the laptop computer shows that the laptop should be used with a 19 V supply.  However, the mains supply is 230 V.  The transformer in the adaptor changes the voltage of the mains to a lower voltage. © Copyright Star Publishing Pte Ltd 18
  19. 19. Transformers  A transformer is an electrical device that changes the voltage of an alternating current (a.c.) supply.  Transformers come in different types and sizes from small ones in laptop adaptors to huge ones at power stations. © Copyright Star Publishing Pte Ltd 19 large transformers are used at power stations
  20. 20. Transformers  A simple transformer consists of two coils of wire wound on an iron core.  One coil is called the primary coil and the other coil is called the secondary coil.  The input voltage is connected to the primary coil and the output voltage is obtained at the secondary coil. © Copyright Star Publishing Pte Ltd 20 a simple transformer € € €
  21. 21. Step-up and step-down transformers  A transformer that increases the voltage is called a step-up transformer while a transformer that decreases the voltage is a step-down transformer. © Copyright Star Publishing Pte Ltd 21
  22. 22. Step-up and step-down transformers A step-down transformer has more turns at the primary coil. A step-up transformer has more turns at the secondary coil © Copyright Star Publishing Pte Ltd 22
  23. 23. Transformers  Transformers work only with alternating current (a.c.) which changes direction many times in one second.  Transformers cannot work with direct current (d.c.) which flows in one direction.  The working of transformer is based on the principles of electromagnetism. © Copyright Star Publishing Pte Ltd 23
  24. 24. Transformers  One important use of transformers is to step-up voltage of electricity at power stations before the electricity is transmitted through cables.  The voltage of the electricity is then stepped down at substations near homes and offices.  Although it may seem troublesome and unnecessary, this process of stepping up and stepping down reduces a lot of energy loss during transmission. © Copyright Star Publishing Pte Ltd 24 Activity Book Link Activity 5.3 Transformers Used in Daily Life
  25. 25. Chapter 5 Sources Of Electricity 5.1 How is electricity generated and transmitted? 5.2 What are transformers used for? 5.3 Why are batteries an important source of energy? 25© Copyright Star Publishing Pte Ltd
  26. 26. Objectives  State the importance of batteries as a source of electricity, giving some examples of their use 26© Copyright Star Publishing Pte Ltd
  27. 27. Electricity from Batteries  Batteries are a portable source of electrical energy.  Some batteries come in standard sizes (e.g. AA size) while others are designed to be used with specific gadgets. © Copyright Star Publishing Pte Ltd 27 standard size batteries laptop batteries a car battery
  28. 28. Electricity from Batteries  The production of electricity using batteries involves energy conversion.  The chemical energy stored in the chemicals in the batteries is converted to electrical energy.  All batteries have 2 terminals, positive (+) and negative (–).  When connected to a circuit, current will flow out from the positive (+) terminal and return to the battery through the negative (–) terminal. © Copyright Star Publishing Pte Ltd 28 each battery has a ‘+’ and a ‘–’ terminal
  29. 29. Electricity from Batteries  When all the chemical energy in a battery is converted, the battery can no longer supply electrical energy. (a) If the battery is non- rechargeable, it has to be thrown away properly. (b) If the battery is rechargeable, it can be used again. © Copyright Star Publishing Pte Ltd 29 during recharging, electrical energy from the mains is converted to chemical energy stored in the battery Activity Book Link Activity 5.4 Batteries
  30. 30. © Copyright Star Publishing Pte Ltd 30

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  • katherinwu

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    May. 4, 2017
  • KebedeTasew1

    Aug. 29, 2019

Uss module 4 chpt 5 Sources of Electricity

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