Question

You are supplied with a galvanometer, resistor, and some connecting wires.

1. Using a circuit diagram, show how will you convert the given galvanometer into an ammeter.

2. Find the expression for the shunt resistance in the circuit.

3. A galvanometer is to be converted into an ammeter of range 0 -1 A. Galvanometer has resistance 100Ω and the current for full-scale deflection is 10 mA. Find the length of the nichrome wire to be used as shunt.

Given, Resistivity ρ = 1.1 × 10^-6 Ωm Diameter of the wire = 1 mm

Answer 1

1. 

2. Let I_g be the current through the galvanometer of resistance RG and the shunt resistance be r_s . Let I be the current to be  measured by the converted ammeter. We can write,

I_gR_G = (I-I_g)r_s

3. Given I = IA

I_g = 10 mA

R_G = 100Ω

Diameter = 1mm

∴ r_s = \(\frac{I_g}{R_G}= \frac{10\times10^{-3}\times100}{(1-0.01)}\) = 1Ω

r_s = \(\frac{ρI}{\pi r^2}\)

I = \(\frac{r_s \pi r^2}{ρ}= \frac{1\times3.14\times(0.5\times10^{-3})^2}{1.1\times10^{-6}}\)

= 0.714 m

\(\phi B.dI = 0\)