CLASSIFICATION OF POWER DIODES:

All Power diodes are classified on the basis of reverse recovery time. Reverse recovery time means time taken to come to off state even after it is turned off. This is because of the minority charge carriers in the diode. Normally during the forward bias condition the holes and electrons move to either side after crossing the depletion region and then conduction takes places. Then some of the minority charge carriers (i.e., electrons) are trapped in the both regions and also in depletion region also. During off state even though we off the diode due to the minority charge carrier’s conduction takes place for some time. This time is called reverse recovery time. These are power diodes which are used for general purposes. Reverse recovery time is (few 10’s to micro seconds). And these are of low frequency. Another one is FAST RECOVERY DIODES in which reverse recovery time is about (30-500 nano sec). Last one is SCHOTKY DIODE in which reverse recovery time is about (< 30 nano sec). In this there is no minority charge carriers flow in reverse biased condition.

HOW SOLAR CELL IS MADE?

The main component for making of solar cell is silica (that is sand). It is heated to 1500⁰C and this forms as a gel. Then this 1500⁰C gel is brought to 0⁰C immediately, so then it becomes hard.  Then we can get glass like material and that to  transparency. By going in to brief  silica is converted to metallurgical grade silicon by coke reduction and then it is dissolved in HCL and then it is send to distillation in which any salts are present that may be removed. Then we get high purity trichlorosilicane. Then it is of poly crystalline silica and it is heated to 1500⁰C we get silicon crystal and these are solids and are made in to pieces by using diamonds and we get silicon pieces. So that’s how solar cell’s are made. There are 36 cells per panel generating of 270 W nearly.

Interesting doubt about ceiling fan

Does ceiling fan rotate even in anti clock wise direction?

Ceiling fans are usually used in every house mainly for cooling the rooms. These fans acts as a blowers and sends the air downwards. The blades of fans are usually at an angle to send air down and are connected to motor inside directly. When we reverse the direction of the fan by changing the winding of the motor it will rotates in opposite direction and acts as an sucker which sucks the air downward and sends to top, usually this is  used in winter  to eject the air in room.  This is about fan with out any reverse direction switches. There is also reverse button switches to run in anti clock wise direction.