JEE Main 2021 · 27 August · evening · Single correct · +4 / −1
The Colour coding on a carbon resistor is shown in the given figure. The resistance value of the given resistor is :
- (a) (5700 ± 285) Ω
- (b) (7500 ± 750) Ω
- (c) (5700 ± 375) Ω
- (d) (7500 ± 375) Ω
Answer and solution
Answer (d) (7500 ± 375) Ω
Solution
Physics sir · 2 steps
Read the bands from the end farthest from gold: two digits, a multiplier, then the tolerance.
- Order of bands. Start from the band nearest one end and keep the gold or silver band last. The first two bands are digits, the third is the power of 10, and the fourth is the tolerance.
Band Colour Meaning Value 1st Violet first digit 7 2nd Green second digit 5 3rd Red multiplier 10² 4th Gold tolerance ± 5% R = 75 × 10² Ω = 7500 Ω, Δ R = 0.05 × 7500 Ω = 375 Ω
- So. The resistance is (7500 ± 375) Ω, which is option (d).
The idea to keep. Use the mnemonic B B R O Y Great Britain Very Good Wife (0 to 9). Gold means ± 5% and silver means ± 10%, always taken as a percentage of the resistance value.
Answer from the NTA final answer key. Solution by PrepWiser.