PN junction diode is a electronic device
which acts like a current passing device in forward bias and acts
like a insulator when it is in the reverse bias. We had already analyzed the
working the of the PN junction diode in the previous post.Here we would like to analyse some more problems on this concept.The core
point that we have to understand is when the voltage applied to the P type
material is more than that of the N type than the diode is in the forward bias
and it is able to pass the current through it .

Let us consider solving the
problem on the concept of a PN junction now.In the following problem we have to identify which of the diode is in forward bias in which of the diode is in reverse
Bias.

In solving the problem we have to
remember only one simple concept that if the voltage that is applied to the P
type material of the PN junction diode is higher than that of the voltage that
is applied to the N type material of the PN junction diode,than the diode is
said to be in the forward bias and vice versa.

Let us solve one more problem on
the same concept. In this problem calculate the current passing in the circuit.

While we are solving this problem
we have to understand that the diode is in the forward bias and it can be able
to pass the current through it. In the case of an ideal diode,the resistance
of the diode in the forward bias is equal to zero.When no information is given in
the problem the shall assume that diode is ideal .

**Problem and Solution**

Let us see one more problem in
solving.In this problem we have to find
the current passing through the hundred ohm resistor.

After having a look at the
circuit we can understand that the diode two is in the reverse Bias and there
is no way that the current is going to passing that diode. Thus that part of the
circuit will become the dead part of the circuit and it is not going to pass
any part of the current through it.

Here we would like to solve one
more problem basing on the diodes and their way of connection. Find the equivalent resistance between the point A and B
as shown in the following circuit.

We need to solve the problem in the two following conditions.

What happens the effective resistance when the voltage at the point A is greater than voltage at the point B and what happens to effective resistance when the voltage at the point B is greater than that of the voltage at the pointy A ?

We need to solve the problem in the two following conditions.

What happens the effective resistance when the voltage at the point A is greater than voltage at the point B and what happens to effective resistance when the voltage at the point B is greater than that of the voltage at the pointy A ?

In solving the problem we are to
be little bit more careful. First of all we had understand that the if diode is in the forward bias it will pass the current through it with the
zero resistance.When the diode is
the reverse Bias it will not pass the current through it.

When the voltage at the pointy A is greater than
that of the voltage at the point B the current the directed from the pointy A
, has two options either to go through
the 18 ohms are to pass to the diode D1. The entire current choose to
pass through the diode D1 because the diode D1 is not offering any resistance
and simply because it is in the forward bias. Current always prefer pass into
the devise ways having less resistance and it will never pass through the
diode who is having high resistance.

when there is an option of having
a devise with zero resistance. Hence the current the distracted from the pointy
a will pass through the diode D1 and then through the diode D2 and then to the
diode D3 and finally reach the point be bypassing all the available
resistances.

Hence the total resistance is
simply sum of all these resistance because they are all in series.The same kind of analysis can be
made even with the second case also.

**Problem and Solution**

Find the current passing through
the battery in the following circuit.

Here also we are going to follow
the same technique.Tthe diode is in forward bias will pass the current in the
diode who is in reverse bias,it will not pass the current is the simple
concept that we need to know to solve this problem.

**Problem and Solution**

Find the equal and resistance
between the point A and B when the
voltage applied at the pointy A is greater than that of the voltage at the
point B.

The analysis of the problem with
is done with the blue colour ink as shown in the diagram below. We had analyse
the problem bit more carefully while we are solving.

What all explanation being written in the diagram itself and we want you to have a look at that and ask the questions that if you have, you can just commented the end of the page so that , we will try to clarify.

What all explanation being written in the diagram itself and we want you to have a look at that and ask the questions that if you have, you can just commented the end of the page so that , we will try to clarify.

**Related Post**

**Distance and displacement**

__comparison__
good collection of conceptual problems sir

ReplyDeleteVery clear explanation.Really helpful for beginners.

ReplyDeletegood explanation

ReplyDelete