When two unknown resistances are connected in series and in parallel,their equivalent resistances are 9 ohm & 2 ohm respectively.What are the two unknown resistances?
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When two unknown resistances are connected in series and in parallel,their equivalent resistances are 9 ohm & 2 ohm respectively. What are the two unknown resistances? In clear stepz plz ! Now, R1+R2 = 9 ohm.14-Jun-2013
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Answer:
Therefore, 6 ohm, 3 ohm OR 3 ohm, 6ohm
Explanation:
Let the Unknown resistances be x and y.
According to question,
In series,
x+y = 9
=> y = 9-x (Equation 1)
In parallel
1/x + 1/y = 1/2
=> x+y/xy = 1/2
(Because, x+y = 9)
=> 9/xy = 1/2
=> xy = 18
From Equation 1
=> x(9-x) = 18
=> 9x - x² - 18 = 0
=> x² - 9x + 18 = 0
=> x² - 6x - 3x - 18 = 0
=> (x-6)(x-3) = 0
=> x = 6,3
y= 9-x = 3,6
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