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        Passive electrical and electronic components

 ThePassive components are devices designed to influence electrical and electronic quantities without returning a gain; in practice, they return a value on their output that is equal to or lower than the value present at their input.

It should be noted that what was said above is mainly valid in direct current, in alternating current it is not always the case, there are some conditions in which a circuit made up of passive components can have a resonance condition, that is, the signal on a single frequency can have a higher value than that at its input, but only on one frequency, the tuning frequency in question is established by the value of the passive components, to find out more you can go to the radiowave page of this site. 

Passive components, usually, in an electric or electronic circuit act as a backdrop to the active components, are used to condition the input and output signals and set the operating parameters of the stages that make up the circuit itself.

The most commonly used passive components are resistors, capacitors, inductors, and fuses.

At the end of this document you will find links to in-depth pages dedicated to Electronic and Active electronic components.

 
 Resistors are electronic components whose value is measured in Ohm (symbol Ω) that serve through the ability to let current pass through them or not, which depends on their value, to obtain the currents and voltages calculated in the design phase at a given point in the circuit. Depending on the current that must pass through them, they are available in various values ​​and powers (and therefore container size).

           
                                  Resistors with their color code
 
                                

                           Electrical symbol of resistance


To establish the value of the resistors, the color code is used as shown in the image below, click on it to enlarge: 


           
                                                               Resistor color Code Table

               
                                                      1400Ω resistor with 5% tolerance


 Reading the code is simple, just look at the first two colors starting from the one closest to the leads (connection terminals) and add as many zeros as indicated by the multiplication coefficient represented by the third color.

Example, we have a resistor with the following colors: brown, black, red, it is read like this: looking at the table we see that brown corresponds to the number 1, black corresponds to the number 0, so we get the number 10, at this point seeing that red corresponds to the number 2 we add two zeros (moltiplication) and our number becomes 10+two zeros=1000, that is 1000Ω.

The fourth colored band represents the tolerance, that is, how much the actual value of the resistor can be moved more or less than the nominal value, for example a 100 Ω resistor with a 5% tolerance can have a real value from 95 Ω to 105 Ω, the lack of the fourth colored band indicates a tolerance of 20% (resistors that have been out of use for many years).

For surface mount resistors (SMD) the value in ohms is printed directly on the body of the component, for example, if the resistor has the number 103 printed on it, it is read like this, first digit 1, second digit 0, the third digit represents the multiplication coefficient by which three zeros are added to the number 10 obtained from the first two digits and we obtain 10000 Ω. The tolerance is not indicated because the maximum deviation from the indicated value in these components is typically less than 5% and therefore its specification is not necessary.

                                                   
                                                                    10000Ω SMD Resistor

There are high power resistors with ceramic body in which the value and power are indicated directly by printing on the container. Resistors are also manufactured whose value can be changed manually (rheostats and potentiometers), and automatic resistors (NTC and PTC sensitive to heat), for further information contact me by visiting the "contacts" page



 Capacitors or electrical capacitances are passive electronic components whose value is measured in Farad (symbol F, the submultiples pF and µF are used) made up of two plates with a dielectric in insulating material in between. They are used to store energy in the form of an electrostatic field and then release it when required. They are used in circuits thanks to their properties of acting as filters, decouplers, phase shifters or phase shifters (because they introduce a delay in the return of the stored signal), as transmission line tuners (see the radiowave page) and their property of blocking direct current and only allowing alternating currents to pass through (exploiting capacitive reactance, i.e. the ability to allow more intense currents to pass through as the frequency increases).

There are various types of capacitors, the most important are electrolytic (used for large capacities), ceramic and polyester, the name is due to the composition of the dielectric (if polyester, it means that the dielectric is made of polyester material, if ceramic, with ceramic material), air can also be used as a dielectric (with obvious limitations). The maximum potential difference applicable to the capacitor depends on the thickness of the dielectric, exceeding causes a destructive event for the component, the perforation or discharge through the dielectric which makes it unusable (short circuit). The maximum voltage of work is stamped on the container together with the capacity and indicated as Vl (Working Volt).
Capacitors whose value is variable are also manufactured (variable capacitors), for further information contact me by going to the "contacts" page
 
                    
                                                     Ceramic and electrolytic capacitors
                                             
                           

                                                  Electrical symbol of capacitors

               
                                                  Polyester capacitors
                 
               
                                                   Surface Mount Capacitors (SMD)

Establishing the value of capacitors is not difficult, you just need to understand the rule, as far as electrolytics are concerned you will find everything clearly stamped on the container including the polarity, yes because you have to be careful, electrolytics are polarized components, you cannot connect them haphazardly, otherwise the component will be destroyed (explosion) which can also be dangerous if it is a high capacity capacitor.

For ceramic capacitors, refer to the table available at this link. For polyester capacitors, refer to the table available at this link. For surface mount chip capacitors (SMD), it is impossible to find the value without using the circuit diagram or the capacitance meter.

The Fuses are components designed to protect electrical circuits, they are simple but important components, there is at least one fuse in every electrical or electronic device. Their function is to interrupt if the intensity of the current exceeds that established by the fuse manufacturer, in practice in the event of a short circuit or other malfunction that causes the current absorbed by any device to rise dangerously, the fuse interrupts and opens the circuit to avoid overheating and fires. There are rapid fuses (which interrupt immediately), semi-delayed (slightly delayed upon interruption) and delayed (there is a pre-established time before interruption) in order to satisfy every need. Self-resetting fuses are also manufactured, but only for small currents.

                    

                                      Various types of fuses

 

                       
                                                            Electrical symbol of fuse


 Passive components are not only those mentioned above, there are many others, among others we can mention:

 The Inductance or coil, exploits the electrical property of inductive reactance to have an impedance that increases as the frequency of the signal passing through it increases.
She is made up of a solenoid wound on plastic material or on a ferromagnetic core, it only works in the presence of alternating signals, its value is expressed in Henry (capital H symbol), in direct current it is nothing more than a wire having a minimum capacity and resistance, which are a parasitic parameter, and must have the lowest possible value, so as not to influence the quality (Q) of the component too much.


The relay is a component that serves to allow the passage or not of a larger electrical quantity using a much smaller signal, it is made up of one or more contacts (switches) controlled by a coil, which when crossed by a current creates an electromagnetic field that attracts or not the contact, the crossing of the coil by an adequate current determines the closing of the contact and therefore the passage of the current through it (larger electrical quantity), while the opening (no current in the coil) interrupts the passage.


 VDRs are components that serve to limit overvoltages that could damage electrical and electronic circuits. They are similar to surge arresters and exist for various operating voltages.
Switches and diverters are simple manually controlled contacts which interrupt the flow of current or divert its path.


 Quartzes are components that use the piezoelectric property of quartz, if we apply an electrical voltage to a piezoelectric material they shrink or expand in a way that is directly proportional to the applied voltage, if instead we apply a pressure to its ends a voltage is established that is directly proportional to the applied pressure, quartzes are used in high frequency to set the oscillation frequency of oscillators, or more generally to make pressure transducers, to learn more you can consult the radiowave page of this site.

 If you want to know more or need professional advice you can contact me through the Contact page.
Below is a series of images that will help you better recognize the components just discussed.
 
                          
               
              Electrolytics, fuses, inductors and resistors of various values
  
               
                                                   In the foreground an NTC resistor

                      

                                                                    Quartz 25 and 14.3 MHz 

                                                                  SMD inductors, capacitors and resistors


Of course it is impossible to condense all these concepts in a small space, mine is only intended to be a good guide for those who are new to this fantastic world, it is however possible to delve deeper or request professional advice by contacting me, for this go to the contact page.

Thank you for visiting my website and following my guide, come back to visit it, you will find new notions and new topics from time to time.

Thank you for visiting my site and happy browsing

 

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