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NTA Abhyas 2020
Exam
NTA Abhyas
Year
2020
Subject
Physics
Chapter
Experimental Physics

NTA Abhyas 2020 · Physics · Experimental Physics

A galvanometer of resistance 50Ω is connected to a battery of 3V...

A galvanometer of resistance 50Ω50Ω is connected to a battery of 3V3V along with a resistance of 2950Ω2950Ω in series. A full-scale deflection of 3030 divisions is obtained in the galvanometer. In order to reduce this deflection to 2020 divisions, the resistance in series should beA galvanometer of resistance 50Ω is connected to a battery of 3V along with a resistance of 2950Ω in series. A

Options

  1. A5050Ω5050Ω
  2. B5550Ω5550Ω
  3. C6050Ω6050Ω
  4. D4450Ω4450Ω

Correct answer

D. 4450Ω4450Ω

Step-by-step solution

Current through the galvanometer

I=3(50+2950)=10−3AI = \dfrac{3}{( 50 + 2950 )} = {10}^{- 3}\text{A}

Current for 30 divisions =10−3A= {10}^{- 3}\text{A}

Current for 20 divisions

=10−330×20=23×10−3A= \dfrac{{10}^{- 3}}{30} \times 20 = \dfrac{2}{3} \times {10}^{- 3}\text{A}

A galvanometer of resistance 50Ω is connected to a battery of 3V along with a resistance of 2950Ω in series. A

For the same deflection to obtain for 20 divisions, let resistance added be R

∴23×10−3=3(50+R)∴ \dfrac{2}{3} \times {10}^{- 3} = \dfrac{3}{\left(50 + R\right)}

orR=4450ΩorR = 4450Ω
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