### Difference between AC and DC

Electricity flows in two ways; either in alternating current (AC) or in direct current (DC). Electricity or 'current' is nothing more than moving electrons along a conductor, like a wire, that have been harnessed for energy. Therefore, the difference between AC and DC has to do with the direction in which the electrons flow. In DC, the electrons flow steadily in a single direction, or "forward." In AC, electrons keep switching directions, sometimes going "forwards" and then going "backwards."

## Comparison chart

Alternating Current
Direct Current
Amount of energy that can be carried
Safe to transfer over longer city distances and can provide more power.
Voltage of DC cannot travel very far until it begins to lose energy.
Cause of the direction of flow of electrons
Rotating magnet along the wire.
Frequency
The frequency of alternating current is 50Hz or 60Hz depending upon the country.
The frequency of direct current is zero.
Direction
It reverses its direction while flowing in a circuit.
It flows in one direction in the circuit.
Current
It is the current of magnitude varying with time
It is the current of constant magnitude.
Flow of Electrons
Electrons keep switching directions - forward and backward.
Electrons move steadily in one direction or 'forward'.
Obtained from
A.C Generator and mains.
Cell or Battery.
Passive Parameters
Impedance.
Resistance only
Power Factor
Lies between 0 & 1.
it is always 1.
Types
Sinusoidal, Trapezoidal, Triangular, Square.
Pure and pulsating.

### 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…