# 5 Lessons Learned: What You Never Knew about Resistors

The three types of resistors include fixed, variable, and physical quality resistors. Materials that resist electricity like carbon composition, carbon film, metal film, thick and thin film, foil, or wire wound to resist electricity are used to make various types of resistors thus they are also classified according to the material that is used to make them.Resistors can be used in many ways besides resisting electric current. Large resistors enable the stored kinetic energy to be released; hence they are used as electric power brakes in trains. They can be used to divide voltage, match and load circuits, generate heat, fix time constraints, and control gain. They are used to power LEDs and blower motors.Read below more information about resistors.

You can identify a resistor using color-coding. The colored bands on the resistor represent its resistance and tolerance values. Most resistors have four colored bands. The colored bands are on the body of the resistor, and they cannot be removed. When you want to know the resistance value of the resistor check the digits that are on the first two bands. The resistance value is determined by the multiplying factor which is shown on the third band. The last band shows the tolerance value.

Colored bands cannot fit on small resistors like the SMDs; therefore, color-coding is not a reliable method of identifying resistors in some cases. Instead of the colored bands; SMDs have a numeric based code. All SMD resistors are of the same size; hence the manufacturing process is standardized for all of them using the rapid-fire pick-and-place machines.

When choosing a resistor, there are three simple steps to follow. First, calculate the resistance that you need using Ohm’s Law using a standard formula. Find out your voltage and current for you to be able to calculate the resistance level of the resistor. The second step is to calculate the power rating of the resistor. The amount of power that the resistor will be dissipating is called the power rating. Use the formula below to calculate the power rating keeping in mind that P (power in Watts), V (voltage drop across the resistor), and R (resistance of the resistor in Ohms). Your LED has a 4V voltage, the resistor has a 200 Ohm value, and the power supply is 10V. The power rating of the resistor is: 10V – 4V = 6V. The 6V is the voltage drop hence calculate the power rating by applying the voltage drop: P = 6V*6V / 200 Ohm = 0.18 Watts. After obtaining the resistance and power rating values, pick a standard resistor that will dissipate the amount of power that you need.

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