Question

A $200\Omega$ resistor has a certain colour code. If one replaces the red colour by green in the code, the new resistance will be
(A) $100\Omega$
(B) $400\Omega$
(C) $500\Omega$
(D) $300\Omega$

Answer 1

In order to solve these types of problems firstly, we have to remember the resistor colour code and after then apply the code in the following format.

Complete step by step answer:
Given that the numerical value of resistance $= 200\Omega$
We know that 2 is the colour code of red colour.
So, according to carbon resistor colour code format

$20 \times 10 = 200\Omega$
Now red is replaced by green colour. Then, we know that the colour code of green is 5. So, the new resistor will be $500\Omega$.
Hence, option C is the correct answer. $500\Omega$

Additional information: In order to solve carbon resistor problems, we must know about the colour code and tolerance of colour i.e.,

Colour	Digit	Multiplier	Tolerance $(\% )$
Black	0	${10^0}(1)$
Brown	1	${10^1}$
Red	2	${10^2}$
Orange	3	${10^3}$
Yellow	4	${10^4}$
Green	5	${10^5}$
Blue	6	${10^6}$
Violet	7	${10^7}$
Gray	8	${10^8}$
White	9	${10^9}$
Gold		${10^{ - 1}}$	$+ 5\%$
Silver		${10^{ - 2}}$	$+ 10\%$
None			$+ 20\%$

Note: Sometimes you may get confused in choosing the correct colour like you may have chosen the first colour as gold or silver from the other end of the resistance so be sure you are choosing the right colour as per the table mentioned above.