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NEET PHYSICSMOVING CHARGES AND MAGNETISMMedium

Question

A moving coil galvanometer has a resistance of 50 Ω50\ \Omega and gives full scale deflection for 10 mA10\ \text{mA}. How could it be converted into an ammeter with a full scale deflection for 1 A1\ \text{A}?

A

50/99 Ω50/99\ \Omega in series

B

50/99 Ω50/99\ \Omega in parallel

C

0.01 Ω0.01\ \Omega in series

D

0.01 Ω0.01\ \Omega in parallel

Step-by-Step Solution

  1. Principle: To convert a galvanometer into an ammeter, a low resistance called a 'shunt' (SS) is connected in parallel with the galvanometer coil. This allows the excess current to bypass the galvanometer .
  2. Formula: The potential difference across the galvanometer (GG) and the shunt (SS) is the same since they are in parallel. IgG=(I−Ig)SI_g G = (I - I_g) S Where: IgI_g = Full scale deflection current of galvanometer = 10 mA=0.01 A10\ \text{mA} = 0.01\ \text{A} GG = Resistance of galvanometer = 50 Ω50\ \Omega
  • II = Desired range of ammeter = 1 A1\ \text{A}
  1. Calculation: Rearranging for SS: S=IgGI−IgS = \frac{I_g G}{I - I_g} S=0.01×501−0.01S = \frac{0.01 \times 50}{1 - 0.01} S=0.50.99=5099 ΩS = \frac{0.5}{0.99} = \frac{50}{99}\ \Omega.
  2. Conclusion: A resistance of 50/99 Ω50/99\ \Omega must be connected in parallel.

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from MOVING CHARGES AND MAGNETISM. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

PHYSICSMOVING CHARGES AND MAGNETISMmovinggalvanometerresistancedeflectiontextma

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