What is a resistor? Free Technical Library article

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Resistors and their application. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Beginner radio amateur

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The most used element in radio engineering devices is the resistor (the old name is resistance). The main characteristic of a resistor is resistance, measured in Omaha. Two types of resistors are available: stable and general purpose. Production of stable resistors is expensive and therefore they are used in expensive high-precision equipment. We will use general purpose resistors. Their resistance can change within 10% (depending on the TCS). Conventional resistors have a TCR (Temperature Coefficient of Resistance) that is positive, meaning that resistance increases with increasing temperature. Only one simple element is negative: carbon.

One of the main characteristics is scatter мощность. Power dissipation is the power that a resistor can dissipate without damage. measured in watts. It is found according to the formula power=current² * resistance.

Each substance has its own resistance, some of them are very large (wood, plastic), others are small (metals, liquids). The resistance depends on the material (for gold, it will be less than that of aluminum), on the length of the conductor (the dependence is direct: the longer the greater the resistance) and on the area of the cut of the conductor (the larger the area, the lower the resistance).

Now let's talk about the use of fixed resistors in circuits. Designation of fixed resistors on circuit diagrams:

	Standard designation
	0,05 W
	0,125 W
	0,25 W
	0,5 W
	1 W
	2 W

If, when assembling the circuit, you did not find a resistor with the required resistance, then you can put two or more resistors in series (their total resistance will be the desired resistance). You can put them in parallel and find their resistance using the formula 1 / R_general = 1/R₁ +1/R₂ +1/R₃.

We will mainly use carbon resistors. If you break it (for the sake of interest, of course) you will see a layer of ceramic covered with a thin carbon film.

Most resistors are marked with color stripes (usually four, less often 5), or a digital designation. For example, 1R means that the resistor has a resistance of 1 ohm, 1.5K - 1.5 kilo ohms (1500 ohms).

There are also variable resistorsthat have the ability to change their resistance. They are used to change the current, voltage, etc. (for example: changing the volume and tone). Most often, the circuit diagram is displayed as follows:

About their types below.

Variable resistors are:

1) single and double

2) single and multi-turn

3) with and without switch

By the nature of the change in resistance:

1) Linear i.e. proportional to the angle of rotation of the axis (group A)

2) Inversely logarithmic, i.e. at first little by little and then sharply increases (group B)

3) Logarithmic (group B)

4) And others (groups E, I)

There are wire and non-wire (film) variable resistors. Wire-wound ones are distinguished by high stability, relatively low level of their noise and low TCR.

In the next issue, we will talk about other important elements - capacitors and transistors. If you have any questions, write to the forum, there is a special section for beginners.

Publication: cxem.net, frikzona.org

See other articles Section Beginner radio amateur.

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