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Std. 7 Electricity

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Published in: Physics
21,322 Views

It consists the information and knowledge about the electricity chapter.

Mirani / Ahmedabad

5 years of teaching experience

Qualification: M.Sc (Gujarat univerrsity - 2014)

Teaches: Mathematics, Physics

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  1. Electricity
  2. Electric circuit An electric circuit is a closed path through which electric current can flow. Necessary condition It must have a source of electric current. A circuit should be closed a continuous path.
  3. A simple circuit contains.... (1 ) Sources of electric current (2) key
  4. (3) Conducting wire (4) An electric device
  5. Diagram of simple electric circuit conventional current flow switch battery light bulb electron flow
  6. Circuit symbol Circuit symbols swiuh $"ltr.h ruist•r ——1
  7. Closed circuit When the path of current start from one terminal of the cell and ends at the other terminal of the cell without any break, the circuit is called complete circuit.
  8. Open circuit when the path of circuit is broken, the circuit is called open circuit larnp voltage switch source zero, zero, zero, zero,
  9. Domestic circuit system Series connection::. Each device is connected in such away that there is only one path to flow for electric current.
  10. Characteristic of series connection All devices work simultaneously in a series connection, when the switch is closed(turned on). Series connection require less wire and are thus economically good. Also, all devices stop working when switch is open. If any one is stopped working then others also stop working.
  11. Parallel connection --There are multiple paths by which electric current can flow. Parallel
  12. Parallel 4000mÅ connection "WAC Series Connection Parallel Connection Why Parallel Connection is Preferred over Series Connection?
  13. All devices function independently. Any device can switch off or on without effecting the working of other devices. any device is out of order the other devices are continuous to work. All the electric appliances installed in the house,factories,offices etc. are connected parallel.
  14. Electrical hazards Overloading-All electrical appliances have certain capacity to draw current from the mains. If too many devices are connected in a circuit then wire draws a much current. Due to large quantity of current more heart is produce.
  15. Short circuit Due to some reason live and the neutral wire touch with each other. This results in a sudden large current flowing through the circuit. This effect is called short circuit.
  16. Safety device in electrical system Electric fuse-An electric fuce is a safety device that protects an electric circuit. (1) The circuit is overloaded (2) If there are fluctuations of current in electrical supply (3) if a short circuit occur
  17. Description of fuse A fuse is essentially a thin wire made of an alloy with a melting point slightly bellow the melting of the conducting wires. Location-lt is fixed between two clamps of copper mounted on a porcelain wires. In domestic circuit the main fuse is usually installed just after the maiin switch.
  18. Pictures of fuse Rernovabte Part Fixed Part
  19. Miniature circuit breakers
  20. Miniature circuit breaker(MCB)- are designed to overcome the trouble in fuse. An mcb is pplaced in the series in the live wire in a circuit and switched on to complete the circuit. Working-Whenever the circuit gets overloaded, the components in the MCB sense the danger, and automatically goes into the off mode.
  21. Earth wire The earth wire plays a important role in electrical connections. All metal bodies of various devices such as electric irons, electric refrigerator , television must be connected with the earth wire. To do this one end is connected to the appliance and other end is connected to earth. Working- In case of leakage current all current will flow to the earth directly
  22. Lightning Arrestor Electrical Service Board THE EAR THING SYSTEM Safe Earthing Electrode Back Fill Compound Building Live Neutral Earth Earth Earth Wire Fault Current Dissipation*' Fault Current Dissipation
  23. Effects of electric current (2) (3) (4) Heating effect Magnetic effect Mechanical effect chemical effect
  24. Heating effect When electric current pass through the conductor heat is produce. Larger current More heat The change of electrical energy into heat energy is called heating effect of electrical current.
  25. Appltcatton of heating effect Heater,geysers,toaster,oven are examples of heating effect of electrical current. The element get heated up when current pass through it. Even when such devices like electric bulb use this effect.
  26. Magnetic effect When electric current is passed through a coil of insulated wire coiled around a soft iron bar, the iron bar behaves as a magnet. This is called magnetic effect of electric current. Magnetic effect disappear as current stoped to flow.
  27. )l)l)l)l)l)l)l)l)l)l)l)l)l)ly
  28. Application of magnetic effect Some of the application of magnetic effect of electric current are.... .... (2) (3) Electric bells Telephones electric cranes
  29. Mechanical effect Flow of electric current through a conductor produce magnetic field. If we put this conductor in magnetic field then two magnetic field interact and movement cause. This effect is called magnetic effect of electric current.
  30. Wbgn electric current passes a coil in a magnetic feed. magnetic force ptot$.jces a torque turns tbe DC motor curtmt a comme•.atc€ curr«t coch keep the e-rni-g tro 'Same
  31. Application of Magnetic effect Electric motors are work on this principle. Fans, food processors and pumps are based on the mechanical effect of electric current.
  32. Chemical effect Copper plate Copper plate Coppcr sulphate soluUon
  33. If electric current is allowed to pass through the solution of certain chemicals. ...it indicate the chemical effect. Exchange of electrons will take place. This effect is called chemical effect of electric current.
  34. Applications Electroplating is commonly used to coat a base metal with a noble metal. Electroplating is used in artificial jewellery.
  35. Conservation of electricity We can conserve electricity by following some simple measure We should switch off electrical appliances when they are not in use. We should energy efficient bulb such as CFLs we need to use solar energy which is the renewable source of energy.
  36. Reflection of light spherical mirror
  37. Spherical mirror-A mirror in which the reflecting surface is curved or spherical is called a spherical mirror. Spherical miror are of the two types (1) Concave mirror (2) convex mirror
  38. Concave mirror-A spherical mirror whose inner surface is reflecting and outer surface is polished is called concave mirror.
  39. Convex mirror-A spherical mirror whose outer surface is the reflecting surface andd the inner surface is polished is called convex mirror. convex mirror focal point
  40. Ray diagram - Image formed by spherical mirrors depend upon (1 ) The nature of the mirror. (2) The distance between pole and object. (3) The focal length of the mirror.
  41. The exact nature and size of the image formed by the object kept at different position in front of the spherical mirror can be known by drawing ray diagram. Rules-The reflecting surface always face towards the left side. The object should kept perpendicular.
  42. OBJECT IS PLACED BETWEEN P AND When the Object is Between the Pole and the Focus
  43. Two incident rays Parallel to the principle axis Ray passing through the centre of curvature Image formed - Image is formed behind the mirror Thus the image formed is virtual, erect and enlarge.
  44. Image formed by the convex mirror. ct Conve rrnrror 13 Irnege
  45. Explanation The image formed by the convex mirror is always virtual,erecet,diminished and formed between F and p.
  46. N/A

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