JEE PYQ: Current Electricity Question 68
Question 68 - 2019 (11 Jan 2019 Shift 1)
In a Wheatstone bridge (see fig.), Resistances P and Q are approximately equal. When $R = 400,\Omega$, the bridge is balanced. On interchanging P and Q, the value of R, for balance, is $405,\Omega$. The value of X is close to:
(1) 401.5 ohm
(2) 404.5 ohm
(3) 403.5 ohm
(4) 402.5 ohm
Show Answer
Answer: (4)
Solution
$\frac{P}{Q} = \frac{R}{X} = \frac{400}{X}$ and $\frac{Q}{P} = \frac{405}{X}$. Multiplying: $1 = \frac{400 \times 405}{X^2}$. $X = \sqrt{400 \times 405} = \sqrt{162000} \approx 402.5,\Omega$.
BETA
