Let’s start with an example. Talk about a Bi-cycle and a Motor Bike.  We don’t have to turn it on in advance to ride or operate a bi-cycle. We can work with it whenever we want. That is, its religion is such that it is always active. So we can call it an active device. But what happens in the case of a motor bike? It must be turned on in order to ride or operate the bike. Moreover it is not able to continue or work. That is, it is not always active. So we can call it, Active Device.

The idea of ​​this active and passive is the same in electronics. There are some components in electronics that do not have to be turned on in advance to be useful. They are always operational. We can use them whenever we want. What we call passive devices. Again, there are many components that have to be turned on like bikes for use at work. What we call active devices.

There are only three passive devices in the whole electronics. E.g.

  1. Resistor
  2. Capacitor
  3. Inductor


The function of a resistor in a circuit is to block the flow of electricity in any situation. No matter which way the electric current flows, it will always give him a barrier. And there is no need to activate it for this work. Like a broken bridge on the road, it always obstructs the traffic and there is no need to activate it. Similarly, the resistor will always block the flow.


The flow of electricity through a circuit means the flow of electrons through it. If we place a capacitor in one place in the circuit, it will take some electrons from the flow of these electrons and store them in itself and provide them when needed. And to do this, you don’t have to turn on the capacitor like a motor bike. So it is a passive device.


Like a capacitor, it is also a passive device. Which when placed in a circuit collects current from the electric current of the circuit and provides it when needed. It does not need to be turned on in advance to activate.

Among the active devices are transistors, microphones, IC etc. For example, to make a transistor operational, it has to be turned on with a voltage beforehand. Which we call biasing voltage.

Jeion Ahmed


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