Civil Engineering World

 

 

  Magnets and Magnetic Fields Magnetic pole  The property of magnet to attract small pieces of iron seems to be concentrated in small regions of   the magnet. These regions are called magnetic poles. A magnet has two poles : i) North pole     and     ii) South pole Magnetic lines of force emerge out from N-pole and converge into S-pole. fig.: Bar magnet  Magnetic Dipole A system of two equal and opposite magnetic poles separated by certain distance is called magnetic dipole. Consider a magnetic dipole consisting of two magnetic poles, north and south each of strength ‘m’ and separated by distance ‘2l’. Magnetic Dipole Moment It is defined as the product of strength of either pole and the distance between the magnetic poles. It is denoted by ‘M’ and given as,        M = m x 2l fig. : Magnetic dipole  The strength of pole ‘m’ is measured in Weber(Wb) or Ampere meter (Am) in SI. Therefo...

  Earth’s Magnetism Our earth behaves as a powerful magnet whose south   pole is towards earth’s north pole and north pole towards the earth’s south pole. It is clear from following evidences ( k|df0fx?+_ M a.        A freely suspended magnetic needle stays in north-south direction. b.       An iron piece buried in earth becomes magnet after a long time. c.        Availability of neutral point. Elements of earth’s magnetism: There are three elements of earth’s magnetism. They are as follows: a.      a.    Angle of declination b.       b.  Angle of dip c.       c.    Horizontal component of earth’s magnetic field a.      a.    Angle of declination The acute angle between the magnetic meridian and the geographical meridian is called angle of declination. Magnetic meridian: The vertic...

  Refraction Through Lenses Lens: A lens is an object usually made of glass bounded by one or two spherical surfaces. Types of lens a .       Convex lens or converging lens A lens is said to be converging lens if the width of beam decreases after refracting through it. It is thick at the middle and thin at the edge. b.       Concave lens or diverging lens A lens is said to be diverging lens if the width of beam increases after refracting through it. It is thin at the middle and thick at the edge. Some terminologies: a.        Center of curvature (C) : Center of curvature of a surface of a lens is defined as the center of that sphere that forms the lens. A lens consists of two radius of curvatures (C 1 and C 2 ). a.        Optical center (c) : The geometrical center of lens is called optical center of lens. b .       Principal axis ...