A galvanometer of resistance $76 \Omega$ gives full scale deflection when only 5% of total current passes through it. The value of shunt is: |
$2 \Omega$ $4 \Omega$ $1.9 \Omega$ $3.8 \Omega$ |
$4 \Omega$ |
The correct answer is Option (2) → $4 \Omega$ The voltage across the galvanometer is the same as the voltage across the shunt resistor. $V_g=I_gR_g$ [Ohm's law] and for shunt Resistor, $V_s=I_sR_s$ and $I_s=0.95I$ because 95% of current pass through shunt resistance. $V_g=I_s$ [given] $I_gR_g=I_sR_s$ $0.05I.R_g=0.95I.R_s$ $R_s=\frac{0.05×76}{0.95}=\frac{3.8}{0.95}≃4Ω$ |