JEE PYQ: Current Electricity Question 36
Question 36 - 2020 (09 Jan 2020 Shift 2)
In a meter bridge experiment S is a standard resistance. R is a resistance wire. It is found that balancing length is $l = 25$ cm. If R is replaced by a wire of half length and half diameter that of R of same material, then the balancing distance $l’$ (in cm) will now be ____.
Show Answer
Answer: 40
Solution
New resistance $R’ = \rho \frac{l/2}{A/4} = 2R$. For meter bridge: $\frac{R}{S} = \frac{l_1}{100-l_1}$, $\frac{R}{S} = \frac{25}{75} = \frac{1}{3}$. $\frac{2R}{S} = \frac{l_2}{100-l_2}$, $\frac{2}{3} = \frac{l_2}{100-l_2}$. $l_2 = 40$ cm.
BETA
