The Science of Electricity

P-N Junction Diode The P-N junction itself forms the most basic semiconductor device called Semiconductor Diode. Thus semiconductor diode and the P-N junction are one and the same. The meaning of the term "diode" is the device having "two electrodes" (di-ode).  As shown in Fig. 1 , the diode has two electrodes one each for the two regions on either sides of the junction. Fig. 1: A P-N junction forms a semiconductor diode  Fig. 2 : Circuit symbol of diode Symbol of the P-N junction diode The symbol of a semiconductor diode is as shown in Fig. 2. The two electrodes (terminals) are named as anode and cathode.  The arrowhead in the symbol points in the direction of conventional current through the device. This current will flow through the diode if and only if an external voltage source is connected to it with appropriate polarities. Biasing of a P-N Junction Diode When the P-N junction is formed, the depletion region gets created and the movement of ele

Semiconductors     Definition : The materials, whose electrical conductivity lies between those of conductors and insulators and have negative temperature coefficient of resistance, are known as semiconductors.   Semiconductor Materials : The few examples of semiconductor materials are as under : 1.Carbon (C) 2. Silicon (Si) 3.Germanium (Ge) 4. Selenium (Se) 5.Gallium Arsenide (GaAs) 6.Cadmium Sulphide (CdS). The commonly used semiconductor materials are Germanium and Silicon. These are tetravalent elements i.e. materials having  four valency.   Atomic Structures of Germanium and Silicon : (i) Atomic structure of Germanium and Silicon atoms :  Fig. 1.3 (b) shows the atomic structure of a Germanium atom  in which first, second, third and fourth orbits have 2, 8, 18 and  4 electrons respectively, with the result that the atomic  number for Germanium is 32. Fig. 1.3 (a) shows the atomic structure of a Silicon atom in  which first, second and th

Introduction :-  If I gave a charge ( either positive or negative) to a particular particle and kept it in a room and what we observed that the charge is moving in a particular direction without being in any contact with anyone or without applying any kind of force. Despite of not applying any kind of force or a contact (by human or by other) to that charge it is moving in a particular direction. But If I took that same charge to a different place or in a different room what we observed? that charge is not moving at all like it was moving in other room instead it is static (not moving).  In some place the charge is moving very rapidly and at some it is very slower; At some places it is moving from left to right at some it  is moving from right to left. But we can't see anything. So what is that force which is driving or moving a charge or applying a force to that charge? What is that unseen thing which is applying force on the charge ? What is that thing in presence