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NCERT Solutions for Class 10th Science

 

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Chapter 13. Magnetic Effects of Electric Current

Chapter Review

 

 

 

Chapter Review:


  • Magnetic field is vector quantity as it has both magnitude and direction. 
  • The natural magnate is known is magnetite.
  • The north needle of compass does not indicate toward the true north exactly, there is some deviation between true north and magnetic north. This deviation of angle between  true north and magnetic north is called magnetic declination. 
  • A coil of many circular turns of insulated copper wire wrapped closely in the shape of a cylinder is called a solenoid. 
  • MRI method works basis on magnetic field presence in the body to get images from the various organs of the human body.
  • Magnetic fields are produced in the human body from flowing ionic current in nervous cells of our body. 
  • The heart and the brain are two human organs which produe magnetic field.
  • Split ring acts as commutator in electric motor. 
  • A device that reverses the direction of flow of current through a circuit is called a commutator
  • The right hand thumb rule Or Maxwell’s corkscrew rule : You are holding a current carrying straight conductor in your hand such that the thumb point towards the direction of current. Then your finger will wrap around the conductor in the direction of the field lines of the magnetic field.  
  • There are two types of current (i) Direct current (D.C) (ii) Alternative current (A.C)
  • In india A.C has 50 Hz as frequency. 
  • Direct current always flows in one direction and it is produced by cell or battery. 
  • The alternating current reverses its direction periodically and it is produced by electric generator. 
  • There is another wire in domestic electric circuit instead of live wire and neutral wire, which has green insulated wire is called the earth wire.
  • The earth wire is used as a safety measure to ensure that any leakage of current to a metallic body does not give any severe electric shock to a user.
  • The process by which a changing magnetic field in a conductor induces a current in another conductor. This process is called the electromagnetic induction.
  • Electromagnetic induction is discovered by Michael Faradey.
  • The direction of field lines is from its south pole and to its north pole. 
  • The magnetic field lines are closed curve. 
  • The relative strength (severity) of magnetic field is shown by the degree of closeness of the field lines. Where the magnetic field lines are crowded, magnetic field is stronger there. 
  • The magnetic field produced by electromagnet is generally very strong.
  • Generally the magnetic field produced by permanent magnet is low and moderate.
  • The polarity of the magnet can be changed by reversing the direction of current in electromagnet. 
  • The polarity of the permanent magnet can not be changed.
  • Normally soft iron is used for making electro magnets.
  • The old convention is red for live, black for neutral and green for earth. The internationally accepted convention is brown for live, light blue for neutral and green or yellow for earth.
  • A compass needle is a small magnet. Its one end, which points towards north, is called a north pole, and the other end, which points towards south, is called a south pole.
  • A magnetic field exists in the region surrounding a magnet, in which the force of the magnet can be detected.
  • 􀂄 Field lines are used to represent a magnetic field. A field line is the path along which a hypothetical free north pole would tend to move.
  • The direction of the magnetic field at a point is given by the direction that a north pole placed at that point would take. Field lines are shown closer together where the magnetic field is greater.
  • A metallic wire carrying an electric current has associated with it a magnetic field. The field lines about the wire consist of a series of concentric circles whose direction is given by the right-hand rule.
    􀂄The pattern of the magnetic field around a conductor due to an electric current flowing through it depends on the shape of the conductor.
  • The magnetic field of a solenoid carrying a current is similar to that of a bar magnet.
  • An electromagnet consists of a core of soft iron wrapped around with a coil of insulated copper wire.
  • A current-carrying conductor when placed in a magnetic field experiences a force. If the direction of the field and that of the current are mutually perpendicular to each other, then the force acting on the conductor will be perpendicular to both and will be given by Fleming’s left-hand rule. This is the basis of an electric motor. An electric motor is a device that converts electric energy into mechanical energy.
  • The phenomenon of electromagnetic induction is the production of induced current in a coil placed in a region where the magnetic field changes with time. The magnetic field may change due to a relative motion between the coil and a magnet placed near to the coil. If the coil is placed near to a current-carrying conductor, the magnetic field may change either due to a change in the current through the conductor or due to the relative motion between the coil and conductor. The direction of the induced current is given by the Fleming’s right-hand rule.
  • A generator converts mechanical energy into electrical energy. It works on the basis of electromagnetic induction.
  • In our houses we receive AC electric power of 220 V with a frequency of 50 Hz. One of the wires in this supply is with red insulation, called live wire. The other one is of black insulation, which is a neutral wire. The potential difference between the two is 220 V. The third is the earth wire that has green insulation and this is connected to a metallic body deep inside earth. It is used as a safety measure to ensure that any leakage of current to a metallic body does not give any severe shock to a user.
  • Fuse is the most important safety device, used for protecting the circuits due to short-circuiting or overloading of the circuits.

     

 

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