Answer: C. 3×104 :1
Two resistors, a and b, have colour codes: orange, blue, white, brown, red, and green. Then the ratio of their resistances a:b is 3×104 :1.
Solution:
Resistor colour coding uses coloured bands printed on the resistor body to calculate the resistance value.
Generally, there will be 3, 4 and 5 colour band resistors; each colour band position and colour will have a particular specification significant value.
The first two colour bands indicate significant value; the third band will indicate multiplier value.
The fourth band indicates the tolerance if present, and if not, the tolerance of that resistor will be 20%.
If present, the fifth band indicates the resistor's temperature coefficient. And Colour coding and its values are shown below table.
Colour | Digit | Multiplier | Tolerance |
Black | 0 | 1 |
|
Brown | 1 | 101 | 1% |
Red | 2 | 102 | 2% |
Orange | 3 | 103 |
|
Yellow | 4 | 104 |
|
Green | 5 | 105 | 0.5% |
Blue | 6 | 106 | 0.25% |
Violet | 7 | 107 | 0.1% |
Grey | 8 | 108 | 0.05% |
White | 9 | 109 | |
Gold |
| 5% | |
Silver |
| 10% | |
None |
| 20% |
So, from the above information, we can calculate the resistance value of resistors a and b.
Resistance of a:
Given colour coding for resistor a: orange, blue, white
So, the resistance of a =36×109 Ω
Resistance of b:
Given colour coding for resistor b: brown, red, green
So, the resistance of b =12×105 Ω
The ratio of resistances a and b =36×109:12×105 =3×104:1
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