INTRODUCTION:
Resistor is a passive component that opposes follow of electric current. It has unit called ohms (Ω) is among the three parameters of ohms low. It has many applications on heat such as water heater, electric iron and ovum. It also used to make high voltage handy and able to control it. It can have other applications, which I will discuss it later in this post.
Now, let discuss about color coding of resistor. Color code is a symbol used to represents rating of the fixed resistor. It gives reliability and tolerance of the resistor. It start from left to right. It can be as follows
4-band color code Resistor:
It consists of first digit, second digit, multiplier and tolerance.
Colors
|
1st band
|
2nd band
|
Multiplier
|
Tolerance
|
Black
|
0
|
0
|
100
|
-
|
Brown
|
1
|
1
|
101
|
-
|
Red
|
2
|
2
|
102
|
-
|
Orange
|
3
|
3
|
103
|
-
|
Yellow
|
4
|
4
|
104
|
-
|
Green
|
5
|
5
|
105
|
-
|
Blue
|
6
|
6
|
106
|
-
|
Violet
|
7
|
7
|
107
|
-
|
Grey
|
8
|
8
|
108
|
-
|
White
|
9
|
9
|
109
|
-
|
Gold
|
-
|
-
|
10-1
|
5%
|
Silver
|
-
|
-
|
10-2
|
10%
|
No color
|
-
|
-
|
-
|
20%
|
What is Tolerance?
Is the rate at which value of resistance change as a result of temperature change This made resistor flexible and have reliability in the circuit.
Example 1:
Determine the complete specification of a resistor having the following colors:
First band- Orange
Second band- Black
Third band- Orange
Fourth band- Silver
Solution:
According to the 4-band color code:
30 x 100 ± 10%
=30,000 ± 10%
=10/100 x 30000= 3000
The resistor minimum value= 30,000-3000= 27,000.
Maximum Value= 30000 + 3000= 33,000.
Therefore 27kΩ and 33kΩ
Example 2, Determine the value of resistor having the stated bands?
1. Red, Red, Orange and Silver.
2. Red, Black, Orange and Gold.
3. Violet, White, Brown and no color.
Solution:
1. 22 x 1000 ± 10%
=22000 ± 10%
=22kΩ ± 10%
10% of 22kΩ
=10/100 X 22000= 2200
For maximum resistor value- 22000 + 2200= 24200Ω. ≈24.2kΩ.
For minimum value of resistor= 22000-2200= 19800kΩ ≈19.8kΩ.
2. Red, Black, Red and Gold.
20 X 100 ± 5%
=2000 ± 5%
5% of 2000
=5/100 X 2000=100
2kΩ + 5%=2000 + 100=2100kΩ ,For maximum resistor value
For minimum resistor value = 2000 – 100=1900kΩ.
3. Violet, White, Brown and no color 79 X 20% = 790 ± 20%
20% of 790
=20/100 X 790=158Ω
Maximum resistor value =790 + 158Ω948Ω.
Minimum resistor value= 790-158=632Ω.
5-band color code Table:
Colors
|
1st band
|
Multiplier
|
Tolerance
|
|
Black
|
0
|
100
|
-
|
|
Brown
|
1
|
101
|
1
|
|
Red
|
2
|
102
|
2
|
|
Orange
|
3
|
103
|
-
|
|
Yellow
|
4
|
104
|
-
|
|
Green
|
5
|
105
|
0.5
|
|
Blue
|
6
|
106
|
0.24
|
|
Violet
|
7
|
107
|
0.1
|
|
Grey
|
8
|
108
|
-
|
|
White
|
9
|
109
|
-
|
|
Gold
|
-
|
10-1
|
5%
|
|
Silver
|
-
|
10-2
|
10%
|
|
No color
|
-
|
-
|
20%
|
Example: Calculate 5-band resistor with, Red, Brown, Blue and white.
Solution:
217 X 106=217MΩ.
Resistor can connected in series or in Parallel as follows:
SPECIAL RESISTORS:
This is types of resistor that performed special task according to the working principle of resistor. They can serve as a switch or sensor.
1. Light Dependent Resistor( LDR):
This is also called Photo resistor, it is light sensitive component that can be used as automatic switch in controlling the light. It is no linear device and it can intrinsic or extrinsic. It latency feature that is, it has resistance recovery rate usually 10ms. But it lack PN junction.
LDR Operation:
It has sensor on its plate which cover with transparence leather, when it going to serve as a switch. For instants, in a street light any time there is darkness, LDR will automatically ON the street light and if there is high light intensity it will OFF the street light. What is secret behind it? Follow me. As I mentioned earlier, LDR is a special type of resistor. Therefore, during darkness the resistor Of LDR goes very low, this will permit flow of current which lead to street light to be ON. Also, during day time or high light intensity, the LDR resistance will go very high. This blocked the follow of current in the circuit.
Thermistor:
I Is a special type of resistor that has sensitivity in temperature change It can be Negative Temperature Coefficient (NTC): This means its resistance decrease as the temperature increase. or Positive Temperature Coefficient(PTC): This means its resistance increase as the temperature decrease.
How to find value of burnt resistor:
1. Scarp the outer coating.
2 . Measure resistance from one end to damaged part.
3. Measure from damaged part to the other end.
4. Add the two values.
Second method by using P=VI.
Where P is POWER measured in Watts. V is voltage measured in Volt and I is current measured in Ampere.
Applications of Resistor in general:
1. As temperature sensor device.
2. Inrush current limiter.
3. In flow measurement.
4. Over-current protection.
5. Self regulating heater.
6. Liquid level sensing.
7. It can use in harsh environment.
8. As time- delay.
9. It used as gas sensors.
10. It is used as detector. e.g. smoke detector.
11. It is used in halogen bulbs.
12. It is used in adjusting signal level. 13. It is used in terminating Transmission line. 14. It is used in heating device. such as water heater and cooker element. 15. Specially designed resistor were used as single-use fuses. | |||||||
