RESISTOR
 |
| Resistor |
Resistors are electronic components, used to reduce, of limit, or resist the flow of current in any electrical or electronic circuit.
RESISTANCE
The property of the resistor to limit the flow of current is known as resistance.
UNIT OF RESISTANCE
The value, or quantity of resistance is measured in units called ohms.
Resistors are called passive devices because their resistance value does not change even when the level of applied voltage or current to it is changed.
The resistance value remains same when the applied voltage is AC or DC.
SOME RESISTANCE VALUE
1000 ohms = 1 kilo ohms
10000 ohms = 10 kilo ohms
100000 ohms = 100 kilo ohms
1000000 ohms = 1 mega ohms
TYPE OF RESISTORS
1) Carbon Resistor
2) Wire Wound Resistor
3) Potentiometer
4) PTC (Positive Temperature Coefficient Resistor)
5) NTC (Negative Temperature Coefficient Resistor)
6) LDR (Light Dependent Resistor)
7) VDR (Voltage Dependent Resistor)
1) CARBON RESISTOR
Carbon is a non metallic ideal material for making a resistor. Resistors made of carbon of graphite are called carbon resistors.
Characteristics of carbon resistor
Merits
1) Their size may be quite small up to 6 mm*1 mm.
2)Their temperature coefficient lies within 0.02 to 0.1 .
3) They are most suitable for high frequency circuits.
4) Their mass may be quite small up to 1 gram.
Demerits
1) Temperature and humidity affect their values.
2)Their stability and reliability are poor.
3) Their current carrying capacity is limited up to 2 watts.
COLOUR CODE CHART
| COLOUR | 1st FIGURE | 2 nd FIGURE | MULTIPLIER | TOLERANCE |
| Black | 0 | 0 | 1 | ------------- |
| Brown | 1 | 1 | 10 | 1% |
| Red | 2 | 2 | 100 | 2% |
| Orange | 3 | 3 | 10^3 =K | 3% |
| Yellow | 4 | 4 | 10^4 | 4% |
| Green | 5 | 5 | 10^5 | ---- |
| Blue | 6 | 6 | 10^6 = M | ---- |
| Violet | 7 | 7 | ----- | ---- |
| Grey | 8 | 8 | ----- | ---- |
| White | 9 | 9 | ----- | ---- |
| Golden | * | * | 0.1 | 5% |
| Silver | * | * | 0.01 | 10% |
| No colour | * | * | * | 20% |
Wire Wound Resistors
These types of resistors are made by winding a wire on an insulated former.
Generally, porcelain pipe piece are used as former and Eureka (60% nickel and 40% copper) is used as resistance wire.
## power rating 5 to 50 watts.
## Resistance are made in the range of 0.01 to 1 mega ohms.
## They have lowest tolerance value up to 5%.
## They have high power rating.
## They have a good stability and reliability.
RHEOSTAT
The resistance value of a rheostat can be varied quite easily.
It is used in Laboratories.
Current control in used.
POTENTIOMETER
A resistor whose resistance value can be varied easily is called a potentiometer.
Potentiometer used in a volume control and tone control in a radio receiver.
Voltage control in used.
PRESET
Voltage control in used.
Comments
Post a Comment
If you have any doubts,please let me know.