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JEE Main 202623 JanuaryEvening Shift
Exam
JEE Main
Year
2026
Date
23 January
Shift
Evening Shift
Subject
Physics
Chapter
Current Electricity

JEE Main 2026 · 23 January · Evening Shift · Physics · Current Electricity

To compare EMF of two cells using potentiometer the balancing...

To compare EMF of two cells using potentiometer the balancing lengths obtained are 200 cm and 150 cm. The least count of scale is 1 cm. The percentage error in the ratio of EMFs is ____\_\_\_\_.

Options

  1. A1.65
  2. B1.45
  3. C1.75
  4. D1.16

Correct answer

D. 1.16

Step-by-step solution

ϵ=λℓ\epsilon = \lambda \ell (Potential gradient)

ϵ1=λℓ1\epsilon_1 = \lambda \ell_1
ϵ2=λℓ2\epsilon_2 = \lambda \ell_2

y=ϵ1ϵ2=ℓ1ℓ2y = \frac{\epsilon_1}{\epsilon_2} = \frac{\ell_1}{\ell_2}

Δyy=Δℓ1ℓ1+Δℓ2ℓ2\frac{\Delta y}{y} = \frac{\Delta \ell_1}{\ell_1} + \frac{\Delta \ell_2}{\ell_2}

Δyy=1200+1150\frac{\Delta y}{y} = \frac{1}{200} + \frac{1}{150}

Δyy×100=(1200+1150)×100=(3+4600)×100=76=1.16%\frac{\Delta y}{y} \times 100 = \left(\frac{1}{200} + \frac{1}{150}\right) \times 100 = \left(\frac{3+4}{600}\right) \times 100 = \frac{7}{6} = 1.16\%
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