Learn about Resistor

What is Resistor?

A resistor is a electronic component through which current passes in a controlled way. So the resistor is an electronic component which creates a resistance in the flow of electric current.

Different forms of resistance:

Carbon film resistor
Metal film resistor
Variable Resistance
SMD Resistance

Resistor Symbols:

Generally there are two standards that are used to denote the symbol of a resistor viz. Institute of Electrical and Electronics Engineers (IEEE) and International Electro Technical Commissions (IEC).

IEEE Resistor Symbol
IEC Resistor Symbol
IEEE Variable Resistor Symbol
Variable Resistor Symbol
IEC Variable Resistor Symbol

The units of resistance is Ohms, which is denoted by Ω omega symbol. The formula for resistance is R = V/I Where V is Voltage drop across the resistor and I is Current flowing through it. It would really be difficult to manufacture the resistors with each and every value. Hence, few values are chosen and the resistors of such values are only manufactured. At the time of designing of new product, the resistors with near values are chosen to match the required applications.

Resistor Colour Code:

The value of a resistor is determined by few coloured ribbon printed on it. A resistor is coated with four or five color bands where each color has a particular value. The below table shows a list of values which each color indicates.

Black 0 1
Brown 1 10 1
Red 2 100 2
Orange 3 1000
Yellow 4 10000
Green 5 100000 0.5
Blue 6 1000000 0.25
Violet 7 10000000 0.1
Grey 8 100000000
White 9 1000000000
Gold 0.1 5
Silver 0.01 10

If the resistor has four colour bands then the first two colored bands represent the first two digits of the resistor value. The third color band is the multiplier i.e number of zeroes as per the third colour band digit added. The fourth color band is the tolerance value.
Tolerance is the range of value within which the original resistor value will be. So the exact value of a 100 Ohm resistor with 5% tolerance may be within the range 95 Ohm to 105 Ohm.

A resistor may also have five color bands. This type of resistors are manufactured with tolerance of 2% and 1% and also for other high accuracy resistors. In these five band resistors, the first three bands represent digits, fourth one represents multiplier and the fifth represents tolerance.

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