The resistance of a galvanometer coil is 3.70 Ohm, and the current required for

Question

The resistance of a galvanometer coil is 3.70 Ohm, and the current required for full scale deflection is 347 Mu A. a) Calculate the resistance of a shunt, R_s, that would convert the galvanometer to an ammeter reading 500 mA full scale. Compute the length of nicrome wire necessary to construct a shunt whose resistance is 0.172 Ohm The diameter of the wire is 2.05 mm and its resistive is 53 times 10^-8 ohm-m The resistance of a galvanometer coil is 11.7 ohm, and the current required for full scale deflection is 267 mA. b) Compute the resistance of the voltmeter multiplier.

Explanation / Answer

4. 500 mA current will divide into galvanometer coil and shunt resistor.

current through coil = I x Rs / (Rs + Rg)

347 x 10^-6 = 500 x 10^-3 x Rs / (Rs + 3.70)

0.347Rs + 1.2839 = 500Rs

Rs = 2.57 x 10^-3 Ohm

b)
Resistance = resistivity x length / cross section area

area, A = pi r^2 = pi (2.05 x10^-3 / 2)^2 = 3.30 x 10^-6 m^2

0.172 = (53 x 10^-8 x L ) / (3.30 x 10^-6)

L = 1.07 m

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