Two Resistance A and B have Colour Codes

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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