### How lightning rod works?

The lightning rod, which Benjamin Franklin invented in 1749, is a metal pole mounted atop a building that draws lightning's electrical charge away from the structure.The rod is attached to an aluminium or copper cable that's connected to an underground conductive grid. This allows the electricity to dissipate harmlessly.
Because lightning tends to strike the tallest object in the vicinity, lightning rods must be taller than any buildings or other objects in the area.If installed properly, a lightning rod will carry a lightning bolt's electrical charge through the path of least resistance along the cable into the ground, reducing the risk of fire or heat damage from the strike.

Lightning looks for the easiest path to travel and lightning rods are good conductors of electrical current. If lightning strikes the rod, the electrical current is moved away from the house and is safely gotten rid of underground. Sometimes lightning strikes and then jumps around a bit, looking for a better path. If a lightning rod is nearby, the lightning can move over to it. This avoids more damage after the lightning has already struck.

### COMMON COLLECTOR CONFIGURATION OF A TRANSISTOR

COMMON COLLECTOR CONNECTION

In  this  configuration  the  input  is  applied  between the  base  and  the  collector and  the  output  is  taken  from  the  collector  and  the  emitter.  Here  the  collector  is common to both the input and the output circuits as shown in Fig.

Common Collector Transistor Circuit

In  common  collector  configuration  the  input  current  is  the  base current  IB  and  the output current is the emitter current IE. The ratio of change in emitter current to the  change in the base current is called current amplification factor.

It is represented by

COMMON COLLECTOR CIRCUIT

A test  circuit  for determining the  static characteristic  of an NPN transistor is shown in Fig. In this circuit the collector is common to both the input and the output circuits.   To   measure   the   base   and   the   emitter   currents,   milli   ammeters   are connected in series with the base and the emitter circuits. Voltmeters are connected   across the input an…