Question : A carbon resistor of (47±4.7)kΩ is to be marked with rings of different colours for its identification. The colour code sequence will be
a) Violet - Yellow - Orange - Silver
b) Yellow - Violet - Orange - Silver
c) Yellow - Green - Violet - Gold
d) Green - Orange - Violet - Gold
Doubt by Deepanshi
Solution :
The given resistance of carbon resistor is
= (47±4.7)kΩ
= (47±4.7)×10³ Ω
= [47×10³ ± 4.7×10³] Ω
= [47×10³ ± 4.7×10³] Ω
Here the value of resistance is given with error limits. So R = 47×10³ Ω and ΔR = 4.7×10³ Ω
From the class XI Chapter - 2, units and measurement you could remember the concept of percentage error. Hence the required percentage error in measurement of Resistance will be
% Error in R = (ΔR/R) ×100
= [4.7×10³ / 47×10³]×100
= [1/10]×100
= 10%
The given value of resistance can also be written as
R = (47×10³ Ω) ± 10%
Now, using the colour coding Table, we can see that
4→Yellow
7→Violet
7→Violet
3→Orange
10% → Silver
10% → Silver
The correct colour code sequence will be Yellow, Violet, Ornage, Silver.
Hence, "b) Yellow - Violet - Orange - Silver" would be the correct option.
