A galvanometer has a coil of resistance 200 Ω with a full scale deflection at 20 μA. The value of resistance to be added to use it as an ammeter of range (0-20) mA is

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(4) 0.20 Ω. S = (I_gG)/(I - I_g) = (20 × 10⁻⁶ × 200)/(20 × 10⁻³ - 20 × 10⁻⁶) S = (4 × 10⁻³)/(0.01998) ≈ 0.20 Ω, in parallel.

A galvanometer has a coil of resistance 200 Ω with a full scale deflection at 20 μA. The value of resistance to be added to use it as an ammeter of range (0-20) mA is

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