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Class VI >> Science >> Electricity and circuits >> Free Detailed Study Notes

ELECTRICITY AND CIRCUITS

IMPORTANT TERMS

  • Electricity - Electricity is the flow of electrical charge or power through a conducting medium like wire.
  • Electric Circuit - An electric circuit is a path along which electricity can flow.
  • Open circuit - The electric circuit in which there is a gap in the connections between the terminals of the cell, wires and the bulb is called an open circuit.
  • Closed circuit - The electric circuit in which there is no gap in the connections between the terminals of the cell, wires and the bulb is called a closed circuit.
  • Switch - the switch is a simple device which is used to open or close a circuit.
  • Source - Source is an external body (living & Nonliving) which provide energy, example: electrical cell is a source of electricity.
  • Electric cell- An electric cell is a device which produces a small amount of electricity.
  • Dry cell – Dry cell is a convenient source of electricity current, consisting semi-solid & dry ingredients.
  • Torch - Torch is a device which is used as a mobile light source.
  • Torch bulb - The small electric bulb which produces light when a torch is switched on.
  • Conductors - Those materials which allow electric current to pass through them.
  • Insulator - Those materials which do not allow electric current to pass through them.

 

Electric Circuit: Electricity is a clean form of energy. In order to make use of the electricity, it needs a circuit to complete the path of current comprising of a source (Cell), a switch and an output device like a bulb.

  • An electric circuit is a path along which electricity can flow.
  • The electric circuits provide a complete path for electricity to pass between the two terminals of an electric cell.
  • Open circuit- The electric circuit in which there is a gap in the connections between the terminals of the cell, wires and the bulb is called an open circuit. This would not allow the free flow of electricity.
  • Closed circuit- The electric circuit in which there is no gap in the connections between the terminals of the cell, wires and the bulb is called a closed circuit. This would not allow the free flow of electricity.
  • Electricity can only flow if there is a complete circuit made of a conductor, such an electric wire, bulb (Output) and a source (cell or power line).
  • Switch- The switch is a simple device which is used to open or close a circuit.

 

Cells:

 

  • Electric cell is a device which produces a small to moderate amount of electricity. A dry cell has two terminals or ends.
  • One end of the cell has a small circular metal cap, which is the positive terminal. It is marked with plus sign (+).
  • Other end of the cell has a flat metal plate, which is the negative terminal. It is marked with minus sign (-).

 

Types of Cells:

Primary Cell - Dry cell, also called primary cell, has chemicals stored in it. Dry cell can generate electricity until the chemicals in the cell are used up. After that, it has to be replaced with a new cell.

 

Secondary Cell - Dry cells that can generate electricity again and again by recharging it, after it gets exhausted, are called secondary cells. Example- Automobile batteries used in vehicles.

 

Button Cell - Button cell are small cell, almost a size of a button. Example- wrist watch, calculator and hearing aids. They cannot be recharged.

 

Solar Cell - A solar cell converts solar energy into electricity.

 

Bulb:

  • A bulb produces light when the electric supply is switched on.
  • The thin wire inside the bulb is known as filament. Tungsten is used as filament.
  • Glowing of bulb- When electric current from the cell passes through the filament of the bulb, the filament gets heated, becomes white hot and starts giving out light.
  • Case of fused bulb – When the filament of a bulb gets excessive supply of electricity, then the thin wire melts and gets broken, thereby cutting the electric supply.

Conductor and Insulators:

  • All metals are good conductors of electricity.
  • Electric wires are made up of copper and aluminum because they are good conductor of electricity.
  • Pure Water is a poor conductor of electricity but when some impurities in mixed in water it behaves as a good conductor since the dissolved ions are good conductors in themselves.
  • Human body is good conductor of electricity as it is made up of 60% - 70% water with dissolved minerals, nutrients etc.
  • Insulator- those material which do not allow electric current to pass through them are called insulator.
  • Rubber, Plastic (polyethylene, PVC, and Bakelite), ceramics, porcelain (china etc.), asbestos, wood, glass, mica, cotton, juice, thermocol, wax, paper, air and most of the gases are insulators.
  • Air is an insulator

Importance of Conductor and Insulator:

  • Conductors are used to carry electricity.
  • Insulators are used for safety.
  • Insulators protect us from getting electric shocks.
  • Insulators allow us to handle current-carrying wires, switches, plug, sockets and other electric appliances safely.

Interesting facts:

  • Electricity travels at the speed of light - more than 260,000 kilometers per second.
  • A spark of static electricity can measure up to three thousand (3,000) volts.
  • A bolt of lightning can measure up to three million (3,000,000) volts, and it lasts less than one second.
  • The first power plant - owned by Thomas Edison - opened in New York City in 1882.
  • It is surprising but true that Ancient Romans recommended touching electric fish to cure headache or gout.
  • The first use of the word ‘electric’ in print made in 1646, originated from the Greek word ‘electron’ meaning ‘amber’?
  •  Thomas Edison invented the electric chair, not as a means of execution but to demonstrate the dangers of electric current.
  • Iceland is the only country where the entire electricity supply comes from renewable sources.