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AIM:  To determine the value of e/m of electron using the bar magnet method. To determine the value of e/m of  electron  using the bar magnet method.   J.J. Thomson, the discoverer of the electron, first determined in 1897 the ratio of the charge  e  of the electron to its mass  m  by applying electric and magnetic fields to a narrow beam of cathode rays. A Cathode Ray Tube (CRT) is a convenient device for determining e/m ratio of the electron. A narrow electron beam is produced in it and the beam can be manipulated by impressed electrical and magnetic fields over a small length of the electron path. The electric field produced by a short length of deflection plates and the magnetic field is applied from outside over the same length. APPARATUS:  A cathode ray tube (CRT), a power supply, two bar magnets, deflection magnetometer, and wooden frame with scales fixed on its arms. FORMULA                                     VD e/m =   ----------------     x 10 11 C/Kg

AIM: a.    To plot forward and reverse characteristics & to determine the cut in voltage of                  a semiconductor p-n diode.            b.   To compare the characteristic curves of germanium and silicon diodes . pn-diode Semiconductors are the materials having very low conductivity in pure form. At ordinary temperatures say at room temperature; few electrons are available in C.B. along with same number of holes in V.B. (a hole or vacancy is created in V.B. when an electron goes from V.B. to C.B. and so this hole is treated as + charge carrier). The conductivity in pure semiconductors is due to both electron and holes. However the number of free charge carriers is too small to have sufficient current. The conductivity of these materials can be increased by adding impurity in controlled manner. The process of adding impurity to pure or intrinsic semiconductors is called doping and the resulting semiconductor is called doped or extrinsic semiconductor. There can be

AIM:  a.   To plot the forward and reverse characteristics of zener diode             b.   To study the voltage regulation action of a zener diode. zener diode These diodes are special purpose diodes. They are heavily doped p-n diode due to which the width of the depletion region is very small. The breakdown voltage of these diodes is very precise and can be fixed to  the desired  value. Beyond the breakdown; the voltage across the diode remains constant. Hence these diodes are specially used as voltage regulators in  d.c.  power supplies. As it acts  as  a constant voltage source, it is often used as a  voltage reference diode . APPARATUS                            a o to 15 V dc power supply, zener diode, voltmeters,  milliammeter FORMULAE                The dynamic resistance of the diode is given by           r z = ∆V z /∆I z THEORY ZENER DIODE : These diodes are special purpose diodes. They are heavily doped p-n diode due to which the width of the de

  AIM:   To determine the radius of the curvature of the convex lens using Newton ’s rings. Newton ’s rings Superposition Principle:  When two or more light waves arrive at a point simultaneously the intensity of the light at that point gets changed. If the light waves arrive in phase (i.e. having zero phase difference) then the point appears bright while if they arrive out of phase, (i.e. with 180 0  phase difference then the point appears dark. Thus a pattern of bright and dark points is obtained APPARATUS: Source of monochromatic light (sodium light), two plane glass plates, Plano-Convex lens, traveling microscope.                      FORMULA:                                   R = m /4 l                                                                   Where m = slope of the line obtained by plotting the squares diameters of rings against                        number of rings.                R = radius of curvature of the convex lens. INTRODUCTION:  S