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For a moving coil galvanometer, the deflection in the coil is 0.05 rad when a current of 10 mA is passed through it. If the torsional constant of suspension wire is 4.0 × 10⁻⁵ N m rad⁻¹, the magnetic field is 0.01 T and the number of turns in the coil is 200, the area of each turn (in cm²) is

Asked in JEE Main 25th Jan 2nd Shift 2023 · Galvanometer sensitivity and figure of merit

• (1) 2.0
• (2) 1.0
• (3) 1.5
• (4) 0.5

Step-by-step solution

Why the other options are wrong

• (1) Doubled the result, for example by using 100 turns.
• (3) Arithmetic slip in the power of ten.
• (4) Halved the result, for example by using 400 turns or 20 mA.

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