Electronics – Basic concepts in electronics

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Electronics – Basic concepts in electronics

electronics programming project

We know that all materials are made up of a large number of atoms and the atom itself is made up of electrons, neutrons, protons and the fundamental particles. The science of electronics is created from the displacement of several electrons among the atoms of matter. The important work of this science is to express methods to control these movements of electrons, in the other words, here we are mostly dealing with electrons.

The electron has a negative charge, and if the number of electrons and protons are equal, the atom is neutral. (Otherwise, it has a positive or negative charge.)

Here, we will not examine how electrons are placed in the atom and why they move somewhere, etc., but we will start with a simple example.

Suppose you are sitting in a room with one open window and one closed window and there is a wind blowing; In this case, you will not feel the wind as much. Now suppose that both windows are open, in this case you will feel the wind blowing. In this case, you can consider the air as the electron, the room as the wire, yourself as the lamp, and the wind as the work that the battery does.

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Battery or power supply

In the battery, chemical reactions produce this force (electron movement force in the wire), and in other generators, this force is supplied from sunlight, electromagnetic induction or…

electronics circuit

You must have noticed that batteries have two poles, positive and negative. These two poles determine the location of electrons (negative pole) and the absence of electrons (positive pole).

Electrons always move to the place where there is no (free) electron or less, that is, they go from the negative pole to the positive; But in the analysis of the circuit, we consider the current from the direction of the movement of the lack of electrons (that is, from the positive to the negative pole).

Relationships and required quantities in electronics

Electric potential: electrical energy stored in a battery or energy produced by an electrical generator. The symbol of electrical energy is U and its unit is Joule (j).

Electric charge: The charge created in an object by losing or gaining electrons is called electric charge, the symbol is q and its unit is coulomb (c), and its value is obtained by the following relationship:

q = n * e –> e~1.6*10^-19 , n: numbers of the electrons

Electric potential difference (voltage): the electric charge flow factor from one object to another and its unit is volt (v) and its symbol is V. You can measure the voltage with a voltmeter (in parallel).

volt electronics

The driving force of the generator (ε): the maximum potential difference that the generator can produce and its unit is volts.

Electric current intensity: the amount of electric charge passing through each section per second, its unit is ampere (A) and its symbol is I, and it is calculated by the following formula:


In the above relationship, t is time in seconds and q is electrical charge in coulombs. The intensity of the current can be measured with an ampere meter (in series).

Electrical resistance: the ratio of potential difference to current intensity, its unit is Ohm (Ω) and its symbol is R. Electrical resistance can be measured with an ohmmeter (in parallel).

The following relationship is a very important relationship in electronics science and is called Ohm’s law:

ohm law

Ampere Hour: it is a unit of charge stored in the battery. Ampere hour is obtained through the following relationship:

ampere electronics

According to the above relationship, if a battery is 60 amp hours, it can keep a 1 amp lamp on with the voltage of the same as the battery for 60 hours.

Electronics parts

A set of components that are used to control the above relationships are called electronics components. There are different types of electronic components and they are usually made of conductive and semi-conductive materials.

Terms and tools in electronics

Short circuit: positive and negative connection in the battery that causes it to discharge. (because the energy spent on the heat inside of the battery, which is made by the internal resistance of the battery, and is wasted)

Ammeter: a device for measuring current intensity that is connected in series in the circuit.

Voltmeter: a device for measuring the potential difference that is connected in parallel in the circuit.

Cycle and frequency: 360 degrees rotation (for example, the rotation of the generator rotor) which is also indicated by 2π, and the number of cycles in one second is called frequency and is indicated by Hz.

Multi-meter: It is a device that can be used as an ohmmeter, voltmeter or ammeter with the help of switches placed on it.

  • It is better to have this device in your possession to run tests.

Circuit: A closed path that can include a power source, communication paths made of conductive materials (such as copper wire), electronic components, etc.

Series circuit: It is a circuit in which parts are connected along each other.

Parallel circuit: It is a circuit in which separate parts are fed for themselves.

Connecting power supplies to each other

Connecting poles of the same name

In order to connect the poles of the same name to each other, we must connect the positive poles to each other and the negative poles to each other, and the following situations occur:

1- The voltage of the sources (batteries) is equal to each other: in this case, the total current intensity is equal to the sum of the current intensity of the batteries, i.e. put the consumer in both desired points (one in + and one in -), the current intensity is equal with this value.

electronics circuit

Vt = V1 = V2 = V3

2- The voltage of the sources is not equal: in this case, the voltage of any source that is lower overcomes the total voltage. (In the first moments, a source with a lower voltage acts like a consumer and may cause damage.)


Vt = V2 = 1v

Connecting opposite poles

In this case, we have to connect the batteries in series so that the positive and negative poles are placed along, and to calculate the total voltage, we have to consider the total potential difference of the batteries.

circuit battery

Vt = V1 + V2 = 1.5+4.5= 6v

  • If in this case the batteries are parallel to each other, a short circuit will occur and cause a violation.

Scientific symbols and conversion of units

In many cases, it is possible that the unit of any quantity is very large or very small, for example 0.0000001 volt, which is very difficult to write, and it is possible that one zero or too many is left in the calculations and disturbs the calculations.

To make it easier to write decimal numbers, you can add a factor of 10 to the negative power of the number you move the decimal point to the right.

For example, we move the decimal point 0.0000001 three digits to the right and write it like this:


For very large numbers, we must put a dot/point at the end and move it to the left by the number of digits we want. We must multiply the resulting number by 10 to the positive power of that number. For example, we want to write the number 1000000 with three digits less, we must act as follows:


Also we can use the following symbols instead of 10 powers:


For example, we can write 10000 volts as 10 Kilovolts.

DC and AC current in electronics

AC current: It is called a current that has an alternating state; That is, the movement of the constant current is increasing and decreasing or positive and negative (phase change). Such as city electricity or input signal to a speaker.


DC current: It is called a current that maintains its voltage stability. This type of current is widely used in low voltage circuits.


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