A galvanometer of resistance 100 Ω gives full scale deflection for 20 mV. Find the resistance to be attached so that it gives full scale deflection of 5 V:

Question

A galvanometer of resistance 100 Ω gives full scale deflection for 20 mV. Find the resistance to be attached so that it gives full scale deflection of 5 V: (A)  24.9× 103 Ω in series (B)  24.9× 103 Ω in parallel (C)  44.9× 103 Ω in series (D)  44.9× 103 Ω in parallel

Tardigrade Admin · Accepted Answer

For full scale deflection for 20 mV. i=(20mV/100 Ω )=0.2 mA Again for full scale deflector of 5 V. (R+100) i=5 V or R+100=(5/i)=(5 V/0.2 mA) =25× 103Ω R=2500-100 24900=24.9× 103 Ω

Q. A galvanometer of resistance $100 Ω$ gives full scale deflection for 20 mV. Find the resistance to be attached so that it gives full scale deflection of 5 V:

$24.9 \times 10^{3} Ω$ in series

$24.9 \times 10^{3} Ω$ in parallel

$44.9 \times 10^{3} Ω$ in series

$44.9 \times 10^{3} Ω$ in parallel

For full scale deflection for 20 mV.
$i = \frac{20 mV}{100 Ω} = 0.2 m A$ Again for full scale deflector of 5 V.
$(R + 100) i = 5 V$ or $R + 100 = \frac{5}{i} = \frac{5 V}{0.2 m A}$ $= 25 \times 10^{3} Ω$ $R = 2500 - 100$ $24900 = 24.9 \times 10^{3} Ω$

Q. A galvanometer of resistance 100Ω gives full scale deflection for 20 mV. Find the resistance to be attached so that it gives full scale deflection of 5 V:

24.9×103Ω in series

24.9×103Ω in parallel

44.9×103Ω in series

44.9×103Ω in parallel