Question

A galvanometer $G$ deflects full scale when a potential difference of $0.50V$ is applied. The internal resistance of the galvanometer $r_g$ is $25$ ohms. An ammeter is constructed by incroprating the galvanometer and an additional resistance $R_s$. The ammeter deflect full scale when a measurement of $2.0A$ is made .
The resistance $R_s$ is closest to :

• A. $0.25\Omega$
• B. $2.5\Omega$
• C. $0.45\Omega$
• D. $1.0\Omega$

Answer 1

The correct option is A $0.25\Omega$

Given:

The data about the galvanometer.

Solution:

we know to costruct ammeter from galvanometer we add shunt of low reistance in paralle with galvano meter.

I=i_g+I_s

I=2,

V across AB =0.50v.

Ig=0.5/25=0.02v

I_s=2-0.02=1.98v

Rs= 0.5/1.98=0.252v

So, correct opt : A