Class 6 Science Chapter 12 Electricity and Circuit, Torch Bulb, Dry Cell, Conductors, Insulators (For CBSE, ICSE, IAS, NET, NRA 2022)

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Electricity and Circuits

Electric Cell

  • It is a device that converts chemical energy into electrical energy.
  • Electricity is produced from the chemicals stored inside it.
  • Electric cell stops producing electricity the moment chemicals in the electric cell are used up. The electric cell has to be replaced with a new one.
  • The car battery is made up of wet cells whereas the cells in in a torch are dry cells.

Electric Circuit

  • The wires passing to and from the electric bulb w. r. t the path defined from one terminal of the electric cell to the other terminal of the electric cell.
  • The direction of the current is taken to be from the positive terminal to the negative terminal of the electric cell.
Electrical Components and Symbols
Open Electric Circuit

In open electric circuit, the electrical contact at any point is broken.

Closed Electric Circuit

In closed electric circuit, the electric current flows from one terminal of a cell or battery to the other.

Direction of Current Flow in an Electric Circuit

Electric Switch

  • It is a simple device that either breaks the circuit or completes it.
  • Electric switches are used in order to either:
    • Stop an electrical gadget in function when required or
    • Start an electrical gadget when required.
  • Electrical gadgets like electric iron, table fan, television set, radio, etc. have switches built into them.
Fubctions of Electrical Components
Column IColumn II
CellA device which produces electricity
CircuitA path of electricity
FilamentGlows when electricity passes in it
BulbConverts electricity into light
SwitchEither breaks or completes a circuit
InsulatorDoes not allow electricity to pass
BatteryA combination of cells
ConductorAllows electricity to pass through it

Dry Cell

  • It is type of electric battery that is commonly used for portable electrical devices and converts chemical energy into electrical energy.
  • It was developed in 1886 by the German scientist Carl Gassner in 1866.
  • It is usually made of metallic cylinder with a flat base which is the negative (-) end of the cell and a metallic cap on top which is the positive (+) end of the cell.
  • Carbon rod with a metal cap on it is the + ve terminal of dry cell.
  • Zinc metal plate is the -ve terminal of a dry cell.

Advantages of a Dry Cell

  • It is light and small.
  • Dry cells are inexpensive.

Structure of a Torch and Torch Bulb

Structure of a Torch
Structure of a Torch Bulb

Fig (a) shows a torch bulb, Fig (b) shows the inside view of a torch bulb.

Experiment

  • A torch can be taken and the bulb inside it can be viewed following which a thin wire fixed in the middle of the glass bulb can be observed.
  • Thereafter the torch can be switched on to observe which part of the bulb is glowing.
  • The thin wire that gives light is known as the filament of the bulb.
  • The filament is fixed to two thicker wires for the support.
  • One of the thick wires is connected to the metal case at the base of the bulb.
  • To the metal tip at the centre of the base, the other thick wire is connected.
  • The metal tip and the base of the bulb are the two terminals of the bulb, fixed in such a way that they don՚t touch each other.
  • The electric bulbs used in homes also have the similar design.

Conductors

  • These are the materials which allow electric current to pass through them.
  • Metals, aqueous solutions of salts (i.e.. , ionic compounds dissolved in water) , graphite, and the human body are the examples.
  • Similarly Copper wire, pencil lead, etc. are conductors.

Insulators

  • These are the materials which don՚t allow electric current to pass through them.
  • Paper, rubber, glass, plastics, etc. are the examples.
  • Similarly, eraser, matchstick, etc. are the insulators.

Power Station

  • Power Stations are responsible for supplying electricity used in our homes.
  • Types of power station:
    • Hydro power station
    • Thermal power station
    • Solar power station
    • Nuclear power station

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