Verified Solution • 2025–26 Session moderate

QJEEM19Ph2ca5: JEE Main 2019 Physics - Class 12 JEEM19Ph2ca5 Solution: A moving coil galvanometer has a coil with 175 turns and area 1 …

A moving coil galvanometer has a coil with 175 turns and area 1 cm2. It uses a torsion band of torsion constant 10–6 N-m/rad. The coil is placed in a maganetic field B parallel to its plane. The coil deflects by 1° for a current of 1 mA. The value of B (in Tesla) is approximately :-

Multiple Choice Options

  • A 10–4
  • B 10–2
  • C 10–1
  • D 10–3

Step-by-Step Verified Solution

NIAB = KQ

175 × 1 × 10–3 × 1 × 10–4 × B = 10−6×π180{{{{10}^{ - 6}} \times \pi } \over {180}}

⇒B=π180×10175≈9.97×10−4 T\Rightarrow B = {\pi \over {180}} \times {{10} \over {175}} \approx 9.97 \times {10^{ - 4}}\,T

⇒\Rightarrow B = 10–3 T

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