### What is the difference between AC and DC Generator?

A generator produces electricity in a form that looks like a linear sine wave: first it is positive and then negative.

To create AC electricity, the central shaft carrying windings - which is called the rotor - has slip rings connected to the ends of the winding. In a single-phase generator (more correctly called an "alternator") the outer slip ring is attached to one end of the rotor's winding and the inner slip ring is attached to the other end of the rotor's winding. (In a three-phase alternator there are three separate windings and three sets of slip rings. Each slip ring is connected to the ends of one pair of the windings in such a manner that no windings are shorted-out.) The slip rings are touched by fixed brushes to take off the AC current.

To generate DC electricity, the central shaft carries a part called a "commutator" which has many separate segments. Each segment in sequence around the commutator is connected to the opposite ends of the rotor's winding . As the rotor spins round, two fixed brushes diametrically opposite one another connect to those segments one by one. Thus, as the rotor spins, one brush always picks up the positive wire from the winding and the opposite brush picks up the negative wire from the winding. So, as the shaft rotates, the two brushes always remain positive or negative.

### 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…