A resistor is a passive electrical component, which offers resistance to the flow of current in a circuit. The capacity to resist the current of a resistor is called resistance and its unit is Ohm(Ω). When it is high the current flow through the circuit low and vice versa. It could be understood well by Ohm’s law. Ie. Voltage, V = I × R, the product of current and resistance. These are used to limit the flow of current in circuits.
The basic principle of resistors is that when connected in series the resistance adds up and when connected in parallel the resistance is lower than the least resistance offered.
DIFFERENT TYPES OF RESISTORS:
The resistance offered by a resistor can be fixed or variable. There are different types of resistors, which have their own advantages and disadvantages. They are classified into different types based on configuration, shape, materials used, manufacturing process and power specifications in the circuit.
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FIXED VALUE RESISTORS:
As the name suggests these resistors have a fixed value of resistance and are the most predominantly used in the circuits. They are manufactured in particular values which are used most often and can be combined (parallel or series) to get the specific value required for your circuit.
VARIABLE RESISTORS:
The variable resistors, also known as potentiometers, are the resistors that can have their value changed either by turning a shaft or in pre-set pots by screwdrivers. It is a three-terminal device, the middle terminal is known as wiper, from where the variable resistance is derived. The other two terminals are the supply terminals for the variable resistor. A coil is wound tightly and the current flow can be limited by rotating the shaft.
The resistance of a resistor is mentioned by the colour code given on the resistor. The colour code has either 4 or 5 rings. The last ring represents the tolerance value with which its resistance could deviate from its manufactured value. Ok, now “Which one is the last ring?”. The spacing between the last two rings will be larger than the spacing between the other rings.
IDENTIFYING THE COLOR CODE OF RESISTORS:
The colour code of a resistor is represented by using ten standard colours which have specific values and a tolerance band is indicated to specify that the resistance can vary within the range.
In four-band colour coding system.
- The first colour ring on the resistor specifies the first digit of the resistance value.
- The second colour ring on the resistor specifies the second digit of the resistance value.
- The third colour ring indicates the tenth power of the specified colours’ band number.
- The fourth one is the tolerance band.
In the above diagram,
1.The first ring colour is brown whose value is 1,
2.The second ring colour is red whose value is 2 and
3.The third ring colour value is 1.
Hence the value can be calculated as,
12 × 10 * (1) which is equal to 120 Ω.
The tolerance band is gold which indicates ±5% of tolerance that is,
120 ± 5% which is, the actual resistance value can be of any value between 115.9 Ω to 124.1 Ω.
In five-band colour coding system.
- The first colour band on the resistor specifies the first digit of the resistance value.
- The second colour band on the resistor specifies the second digit of the resistance value.
- The third colour band on the resistor specifies the third digit of the resistance value.
- The fourth colour band indicates the tenth power of the specified colours’ band number.
- The fifth one is the tolerance band.
The power rating of a resistor can be identified by the size of the resistor which can be quarter watt, half-watt or one watt.
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