There are fixed, variable, and physical quality resistors. They are made of carbon composition, carbon film, metal film, thick and thin film, foil, or wire wound to resist electricity. Resistors have more uses 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.
Color-coding is the easiest way of identifying resistors. The resistance and tolerance values of a resistor are displayed by several colored bands. Most models of resistors are made with four colored bands. The colored bands cannot e removed because they are integrated into the body of the resistor. The resistance value is represented by the digits that are on the first two bands. The digits on the third band show the multiplying factor which is a vital element in calculating the resistance value of the resistor. The tolerance value of the resistor is engraved on the last band.
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.
If you are planning to buy a resistor, please use these guidelines. The first step is to use a standard formula and Ohm’s Law to calculate the resistance of the resistor so that you are assured that it has the resistance level that you need. Know your voltage and current for you to calculate its resistance level. Your second step will be to calculate the power rating of the resistor. The amount of power that the resistor will be dissipating is called the power rating. You can use the example below to calculate the power rating where 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 resistor’s power rating will be: 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. Buy a resistor that will fulfill your objectives after you get the resistance and power rating values because these values should guide you to get the most suitable one.