Information Technology

 Magnet:  (i) is an object that attracts objects made of iron, cobalt & nickel. (ii) Comes to rest in North-South direction, when suspended freely. ? Magnets are used:  (i) In radio & stereo speakers, (ii) In refrigerator doors, (iii) on audio & video cassettes players, (iv) On hard discs & floppies of computers & (v) in children's toys. ? Magnetic field:  The area around a magnet where a magnetic force is experienced is called a magnetic field. It is a quantity that has both direction & magnitude. ? Magnetic field lines:  Magnetic field is represented by field lines. They are lines drawn in a Magnetic field along which a North magnetic pole moves. Magnetic field lines are called as Magnetic lines of force. Properties of Magnetic field lines: (i) They do not intersect each other. (ii)  It is taken by convention that magnetic field lines emerge from North pole and merge at the South pole. Inside the magnet, their direction is from South pole to Nor

1. Positive and negative charges:  The charge acquired by a glass rod when rubbed with silk is called positive charge and the charge acquired by an ebonite rod when rubbed with wool is called negative charge. 2.Coulomb:  It is the S.I. unit of charge. One coulomb is defined as that amount of charge which repels an equal and similar charge with a force of 9 x 10 9  N when placed in vacuum at a distance of 1 meter from it. Charge on an electron = -1.6 x 10 -19  coulomb. 3 Static and current electricities:  Static electricity deals with the electric charges at rest while the current electricity deals with the electric charges in motion. 4.Conductor:  A substance which allows passage of electric charges through it easily is called a ?conductor. A conductor offers very low resistance to the flow of current. For example copper,silver, aluminium etc. 5.Insulator:  A substance that has infinitely high resistance does not allow electric current to flow through it. It is called an ?