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Current Electricity question

2024 · 27 Jan · Shift 2 · Q79
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Current Electricity question

2024 · 27 Jan · Shift 2 · Q79

JEE MainPhysicsCurrent ElectricityMCQ+4 / −1
A current of 200μA200 \mu \mathrm{A}200μA deflects the coil of a moving coil galvanometer through 60∘60^{\circ}60∘. The current to cause deflection through π10\frac{\pi}{10}10π​ radian is :
  1. A
    120 μ\muμ A
  2. B
    180 μ\muμ A
  3. C
    30 μ\muμ A
  4. D
    60 μ\muμ A
View written solutionFree

Correct answer: D

  1. Use the property of a moving coil galvanometer

    For a moving coil galvanometer, the deflection θ\thetaθ is directly proportional to the current III: I∝θI \propto \thetaI∝θ Hence, I1I2=θ1θ2\frac{I_1}{I_2} = \frac{\theta_1}{\theta_2}I2​I1​​=θ2​θ1​​

  2. Given data

    • Current I1=200 μAI_1 = 200\,\mu\text{A}I1​=200μA
    • Deflection θ1=60∘\theta_1 = 60^\circθ1​=60∘

    Required deflection: θ2=π10 rad\theta_2 = \frac{\pi}{10}\text{ rad}θ2​=10π​ rad

  3. Convert units so both angles are in the same unit

    Since 180∘=π rad180^\circ = \pi \text{ rad}180∘=π rad therefore, π10 rad=180∘10=18∘\frac{\pi}{10}\text{ rad} = \frac{180^\circ}{10} = 18^\circ10π​ rad=10180∘​=18∘

  4. Apply proportionality

    I1I2=θ1θ2\frac{I_1}{I_2} = \frac{\theta_1}{\theta_2}I2​I1​​=θ2​θ1​​

    200I2=6018\frac{200}{I_2} = \frac{60}{18}I2​200​=1860​

    So, I2=200×1860I_2 = 200 \times \frac{18}{60}I2​=200×6018​

    I2=200×310=60 μAI_2 = 200 \times \frac{3}{10} = 60\,\mu\text{A}I2​=200×103​=60μA

  5. Match with options

    60 μA60\,\mu\text{A}60μA corresponds to Option D.

Final Answer: 60 μA60\,\mu\text{A}60μA

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