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JEE Main 2020 (9 Jan, Shift 2) · Wheatstone Bridge & Metre Bridge

Wheatstone Bridge & Metre Bridge question from JEE Main 2020 (9 Jan, Shift 2)

Q64JEE Main 2020 · 9 JAN · SHIFT 2Medium

Wheatstone Bridge & Metre Bridge

In a meter bridge experiment S is a standard resistance. R is a resistance wire. It is found that balancing length is ll = 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′l' (in cm) will now be________.

Figure

Numerical answer type. Work it out, then open the answer.

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Answer: 40

  1. RS=2575=13\dfrac{R}{S} = \dfrac{25}{75} = \dfrac{1}{3}.
  2. R∝Ld2R \propto \dfrac{L}{d^2}: half length and half diameter give R′=1/21/4R=2RR' = \dfrac{1/2}{1/4}R = 2R.
  3. R′S=23=l′100−l′⇒l′=40 cm\dfrac{R'}{S} = \dfrac{2}{3} = \dfrac{l'}{100-l'} \Rightarrow l' = 40\text{ cm}.
  4. l′=40 cml' = 40\text{ cm}.
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