P-N JUNCTION DIODE

P-N JUNCTION DIODE :-

It is one of the most usable electronics element . It is made up of semiconductors of p- type and n- type, when we join both semiconductors it forms a junction between them, hence the junction is from this name.

This device has two terminals / electrodes one from n-type semiconductor and second from p-type semiconductor . Due to the two electrodes it is called DIODE, i.e. di + electrode.

To connect the external terminals , a metal is applied to the heavily doped n-type and p-type semiconductor. which is called ohmic contact.
The drop across the contact is very small which do not affect the performance of the device.

DIAGRAMS AND SYMBOLS :-

p-n junction diade

symbol

BIASING :- 

To operate the diode we need to know about the biasing .

our diode works short circuit when it is in the forward biased, means it pass current on it.
and when it is reverse biased it act as a open circuit, means it do not allow to pass current on it.
FORWARD BIASING:-
the p terminal of diode is connected to the positive terminal of the battery and the n terminal of diode is connected to the negative terminal of the battery.
shown the fig.


REVERSE BIASING:-
the n terminal of diode is connected to the positive terminal of the battery and the p terminal of diode is connected to the negative terminal of the battery.
shown the fig.

USE OF DIODE :-

It allow to flow current only in one direction so it is use in rectifier circuits.
And also to send information or signal in only one direction.

What is an LDR ? || How to use it in the circuit.

LDR :-

LDR is light-dependent resistor . It is a kind of variable resistance . It very automatic with respect to light . we can control it`s resistance with the help of light intensity.

It works on the photo-conductivity principle , and it is a passive element of electronics circuit .

Image of an LDR

It is made of a high resistance semiconductor.

Material use to make It ?

It is made from Semiconductor material , Which have most light Sensitive properties.

Mainly most of the LDR made up of Cadmium Sulphide ,(CdS)

VIDEO:-

IT`S RESISTANCE :-

In the time of dark means when LDE in the dark (low light intensity) it show high resistance in Mega ohms .
{so light intensity is inversely proportional to the resistance of LDE.}

And in the time of light means the intensity of light is high , so LDE show very low resistance in the order of ohms only.

UNIT OF LDR :-

It is a kind of resistance so its unit is same as resistance

which is OHM  𝞨 .

USE OF LDR :-

LDR is also a light sensing element in electronics.

* To make night light :-
It is a electric circuit which is made with the help of LDR. This circuit is use as a automatic switch.
When light fall on this circuit it off automatically and when the light intensity decrease on this circuit it on automatically.
[this circuit is works on both directions...]

We can use LDR in any light detecting circuits .
Like Light depending alarm system , Light depending switch , Light depending indicators ect.

RESISTANCE :-

RESISTANCE :-

It is the basic element of electrical and electronics instruments and machines .
Resistance can be define as a barrier in the way / path of current
in conductor (It is a single straight wire.).
We have a formula for finding the value of resistance , it is given
by scientist OHM . that is :-

V = IR                                                                                     R = V/I

It is Ohm`s law
where R = resistance of the conductor.
  V = voltage of the terminals of the conductor.
  I = current flowing in the conductor.

We can say that the ratio between voltage and current is define as resistance.

DIAGRAMS AND SYMBOLS OF RESISTANCE :-

Symbol of resistance are shown in fig. below;
We can use the symbol of resistance at the time of
circuit draw in paper.

  

SYMBOL

                                     

UNIT OF RESISTANCE :- 

Here the unit of resistance is OHM , is symbolic representation is
Greek word (omega) Ω

Where ohm = volt / ampere ;

USES OF RESISTANCE :-

Basically we use resistance to reduce current in some electronics
device.
1.) To protect device.
2.) Safety purpose.
3.) To reduce voltage.

VARIABLE RESISTANCE :-

this is A kind of resistance, but it can increase or decrease its
resistance.
is symbol and fig. shown below.

SYMBOL