REAL COMPONENTS

Basic Circuit Elements



Basic Circuit Elements

Resistors

The most used element in a radio device - a resistor (the old name - the resistance). The main characteristic of the resistor - resistance is measured in ohms. Available in two types of resistors: a stable and general purpose. Production of stable resistors expensive and therefore they are used in expensive high-precision equipment. We will use the general purpose resistors. Their resistance can be changed within 10% (depending on the TCR). In ordinary resistor TCR (Temperature Coefficient of Resistance) that is positive with an increase in temperature increases the resistance. Only one item, it is a simple negative: the carbon.

One of the main characteristics is the power dissipation. Power dissipation is the power which the resistor can dissipate without damage. It is measured in watts. Found by the formula power = current * resistance .

Each substance has its own resistance, in some it is a very large (wood, plastic), the other small (metals and liquids). The resistance depends on the material (in gold, it will be less than that of aluminum) on the length of the conductor (direct relationship: the longer the greater the resistance) and from the area of ??the cut wire (more so than the area of ??resistance is less).

Now let's talk about the use of resistors in the circuit constants. Designation of Permanent rezistrorov on the schematic:

Standard notation

0.05 W

Tues 0.125

0.25 W

0.5 W

1 W

2 W

If the assembly scheme you can not find a resistor with a resistance fit you can put two or more resistors in series (total resistance and they will fit the resistance). You can put in parallel and find their resistance by the formula 1 / R obsh = 1 / R 1 +1 / R 2 + 1 / R 3.

Basically, we use carbon resistors. If you break (for the sake of interest, of course) you will see a layer of ceramic coated with a thin carbon film.

Most of the resistors labeled color stripes (usually four, rarely five), or digital representation. For example 1R means that the resistor has a resistance of 1 ohm, 1.5K - 1.5 kilohms (1500 ohms). To determine the resistance of the color bands can use the program "Rezistor", you can download it under " Programs "

There are as variable resistors, and possessing the ability to change its resistance. They are used to change the current, voltage, and others (such as changes in volume and timbre). Most often in the schematic diagram shown as follows: About their types below.

Variable resistors are:

Single and double 

2) single and multi- 

3) with the switch and without the

By the nature of the change in resistance:

1) Linear ie, proportional to the angle of rotation axis (group A) 2) Conversely logarithmic, ie, first slowly and then sharply increases (group B) 3) Log (Group B) 4) and others (group E, I)

There are wire and wire (film) variable resistors. Wire are very stable, relatively low levels of noise and their low TCR.

Color code

There are three types of resistors: those with 4 rings, 5 rings and 6 rings. For resistors 5 and 6 rings, the first three rings give significant digits, the fourth gives the multiplier (power of 10 with which we must multiply the significant digits). For resistance to 4 rings, the rings are the first two significant digits and the third ...