A galvanometer of resistance $76 \Omega$ gives full scale deflection when only 5% of total current passes through it. The value of shunt is:
Answer & explanation
Correct answer: option 2
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]
$I_gR_g=I_sR_s$
$0.05I.R_g=0.95I.R_s$
$R_s=\frac{0.05×76}{0.95}=\frac{3.8}{0.95}≃4Ω$