# Resistor

**Resistor **– a double-ended, passive electronic component. It is a linear component meaning that the voltage drop is directly proportional to the current that flows through it. Resistor is used to reduce or achieve the desired value of the current that flows in the electrical circuit. It is used to work in direct, alternating or pulse current (a type of circuit has a significant impact on its properties). Memory resistor (that is controlled by current) is called **memristor**.

There are plenty of applications for resistors:

- in
**amplifiers**– as elements of feedback, - in
**transistors**– to set the operating point, - in
**signal-filtering devices**– combined with**capacitors,** - broadly defined electrical circuits.

Resistor with adjustable electrical resistance is called a **potentiometer**. It is a triple-ended element used as the voltage divider.

**The main parameters that characterize resistor**:

**nominal resistance**(conductance is often used in Siemens) – given by the manufacturer on the housing element that can be measured using a multimeter,**accuracy class**(tolerance) – possible deviation of the actual value of the resistor from the nominal value (given in percentages),**power rating**– the maximum permissible power that can be spun off as heat from resistor under certain conditions,**temperature coefficient of resistance**(**TCR**) – it defines resistance variation under the influence of temperature (the smaller the TCR, the more stable resistor is),**voltage limiting**– the maximum value of the voltage item on direct current (or the highest effective value of alternating current), that won’t cause any damage. The value depends on the material from which resistor was made eg. for common low power range resistors it’s 150 to 500 V.

**Resistor symbols:**

**Formulas and issues associated with the element:**

**R = U / I**

**I. Ohm’s Law**

**I. Ohm’s Law**

**R**– the resistance (Ω – Ohm)

**U(V)** – the current between the element ends (**V**– Volt)

**I **– current (**A** – Amperes)

**P = U * I**

**II. The power dissipated on the resistor**

**II. The power dissipated on the resistor**

**P **– electric power (**W** – Watts)

After switching equation number one on the form: **I = U/R** it can be noticed that with determined voltage value, by changing resistor value, the value of the current flowing though the device is changed (and vice versa – in accordance to the “triangle” above). Therefore, we can risk saying that this is an element that is used to process voltage current (and vice versa).

**III. Series resistors**

In the** series** connection, the total resistance is the sum of the individual values.

**R = R1 + R2 + …Rn**

**IV. Parallel resistors**

For two, parallel connected resistors the total resistance pattern is written as:

**R = R1,2 = R1 * R2 / R1 + R2**

*V. Voltage divider*

*V. Voltage divider*

**Voltage divider** – two resistors in series connection. It is used to separate the voltage supplied to its input, so its output voltage is part of the input voltage. Input voltage is supplied to the R1 and R2 resistors, while the output voltage is equal to the voltage drop on the resistors R2:

**Uwy = Uwe * R2 / R1 + R2**

This is really the first article I read about resistors but it seams they are used in many areas of life and according to me can be a valuable source of information. It looks like a resistor can provide information about bigger then expected flow of energy by changing its temperature. I guess…!!??

The “bigger” the current is “flowing” through the resistor, the more heat it gives back as a side effect of this phenomenon. This “side effect” is desired in many devices e.g heaters… but in the other way high temperature is a serious problem in devices that are vulnerable to it and placed in enclosures.

Whoever wrote this, you know how to make a good arctcle.