Page 108 - Physics - XII
P. 108

Observations

              The resistor, capacitor, diode, and LED are all two terminal devices.
                 S. No.   Possibility of current fl ow                                            Component

                   1.     Current in one direction only and emits no light                          Diode

                   2.     Current in one direction only and emits light                              LED

                   3.     Current in both directions                                               Resistor

                   4.     Given initial defl ection which decays to zero                            Capacitor


              Result

              A diode, a LED, a resistor, and a capacitor are identifi ed one by one from the given collection of items.

              Precautions
              While checking any component, clean its leads properly by using a sand paper so that the insulation

              can be removed.

                                                         ACTIVITY - 2

              Aim
              Use of multimeter to see the unidirectional fl ow of current in case of a diode and an LED and check
              whether a given electronic component (e.g., diode) is in working order.

              Apparatus and Materials Required

                Diode, LED, and multimeter

              Principle/Theory
              Multimeter is an instrument used for measuring current in amperes, voltage in volts, and resistance in ohms.
              Therefore, it is also known as an AVO meter. Diff erent ranges for measurement of diff erent parameters can
              be selected by arrangement of a rotatory switch. Multimeter has two leads, black and red, each lead has a
              metallic end.

              Procedure
              Adjustment of the Multimeter

              1.  Take  the  multimeter  and  plug  in  the  smaller  probes  of  testing  leads  into  jack  socket  marked  as
                  positive (+) and negative (–).
              2.  Turn the selector switch in the resistance region, so that it points towards X MΩ or X KΩ and now
                  adjust zero ohm switch, till the pointer of multimeter comes to zero mark of the resistance scale, when
                  the two probes (leads) short circuited. In this manner, multimeter is set as an ohmmeter.
              To see the unidirectional fl ow of current through it
              (a)  For Diode

              3.  Connect the two leads of the multimeter to the two terminals of the junction diode and note whether
                  the resistance of junction diode is low or high. Now, interchange the two leads of multimeter to the two
                  terminals of the diode and again note whether the resistance of the junction diode is low or high.

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