Bipolar Junction Transistor As a Switch

Switching:

The Bipolar junction transistors can also be used for switching in a circuit. It means that we can use BJT as for current controlling switch. The current in the base will decide whether the current will flow from emitter to collector or not, that’s how it can be used as switch. BJT in circuit used for switching the high voltage or high power circuit with the very low power control variable. We will try to figure it out with the help of example.

Example of BJT as Switch:

As shown in figure below simple lamp circuit with a battery. As switch is open then lamp is off as in fig (1), while when switch is closed, the circuit is closed and lamp is glowing in fig (2).

Fig (1)

Fig (2)

Now when we used bipolar junction transistor in place of switch in above circuit and connect a 1 K resistor with base to provide some current for the base. NPN type of Bipolar junction transistor is being used in this circuit. PNP could also be used, it is just difference of polarity in connections. Keep in mind that the direction of flow of current should be opposite to the direction of arrow on emitter of BJT. The direction of current flow is shown by red arrows in fig (3).

Fig (3)

The BJT do switching in between two state regions; cut off region and saturation region. When there will be no resistor connected with base or if there is open circuit at base of BJT, then the flow of current from emitter to collector will not occur and transistor would be in its “cut off” state. And thus lamp will not glow.

While when there will be resistance connected with the base, some current will flow through base (where we have studied before base current is controlling current). When there will be current through base then current will pass through collector and lamp will glow up and transistor would be in "saturated" state.

So we have seen that we can do switching of high level with the very small amount of current in base. That’s a big advantage of having a BJTs.

Applications:

Due to this switching property of BJT, it has many application in industry and smart production.

1. In a thermocouple circuit, we can use BJT as switch while taking heat as a source for base current. So that with heat on switch on.

2. In automatic door, with the presence of a person near the door, will initiate the base and switch will open.

Like these it has many application in this era.

Electric Motor(AC)

Definition:-

"An electric device that converts an AC electric source into mechanical energy is known as AC electric motor"

The device that converts Electrical energy into mechanical energy for our use, we called that device electric motor.

Explanation:-

The above diagram is of ac motor that converts an ac source into mechanical energy. The problem we face in ac motor is that, ac current changes its direction after half cycle. So it is not possible for conducting coil to move in one direction for complete cycle of  ac current. To overcome this problem, we use split rings instead of commutator, so that we could reverse the direction of current. and coil could move in one direction.

Construction:-

It consists of,

1.Magnet

2.Conducting loop

3.Split rings

4.Carbon brushes

5.Ac source

Working:-

AC motor works on the same principle, as DC motor works. When we connect ac current source to the carbon brushes then through split rings current starts to flow through the wire( or conducting loop) so because there is also magnet field through wire and now current flowing through it, So according to Fleming's left hand rule, the coil will start to move. When ac current will change its direction split rings will change their direction and so coil will get same directed current and coil will move in one direction.

Linked list

Linked list

Definition:

a linked list is a linear collection of data elements, in which linear order is not given by their physical placement in memory. Each pointing to the next node by means of a pointer. It is a data structure consisting of a group of nodes which together represent a sequence

Explanation:

A linked list is a linear data structure where each element is a separate object.

Each element of a list is comprising of two items - the data and a reference to the next node. The last node has a reference to null. The entry point into a linked list is called the head of the list. It should be noted that head is not a separate node, but the reference to the first node. If the list is empty then the head is a null reference.

A linked list is a dynamic data structure. The number of nodes in a list is not fixed and can grow and shrink on demand. Any application which has to deal with an unknown number of objects will need to use a linked list.

There are some figures below to explain Linked list.