Question

A teacher in his physics laboratory allotted an experiment to determine the resistance (G) of a galvanometer. Students took the observations for $\frac 13$ deflection in the galvanometer. Which of the below is true for measuring value of G?

• A. $\frac 13$ deflection method cannot be used for determining the resistance of the galvanometer.
• B. $\frac 13$ deflection method can be used and in this case the G equals to twice the value of shunt resistance(s).
• C. $\frac 13$ deflection method can be used and in this case, the G equals to three times the value of shunt resistance(s).
• D. $\frac 13$ deflection method can be used and in this case the G value equals to the shunt resistance(s).

Answer 1

Answer: (B)

$\frac 13$ deflection method can be used and in this case the G equals to twice the value of shunt resistance(s).

Answer 2

The circuit for the given situation is:

Since G and S are in parallel,
$\frac i3 \times G = \frac {2i}{3} \times S$
$G = 2S$
So, G equals twice the value of shunt resistance.

Hence, the correct option is (B): $\frac 13$ deflection method can be used and in this case the G equals to twice the value of shunt resistance(s).