Magnetism Question 107
Question: A certain amount of current when flowing in a properly set tangent galvanometer, produces a deflection of 45°. If the current be reduced by a factor of $ \sqrt{3} $ , the deflection would
[MP PMT 1996; DPMT 2005]
Options:
A) Decrease by 30°
B) Decrease by 15°
C) Increase by 15°
D) Increase by 30°
Show Answer
Answer:
Correct Answer: B
Solution:
In tangent galvanometer, $ I\propto \tan \theta $
$ \
Therefore \ \frac{I _{1}}{I _{2}}=\frac{\tan {\theta _{1}}}{\tan {\theta _{2}}}\Rightarrow \frac{I _{1}}{I _{1}/\sqrt{3}}=\frac{\tan 45^{0}}{\tan {\theta _{2}}} $
$ \Rightarrow \sqrt{3}\tan {\theta _{2}}=1\Rightarrow \tan {\theta _{2}}=\frac{1}{\sqrt{3}}\Rightarrow {\theta _{2}}=30^{o} $ So deflection will decrease by 45o- 30o = 15o.
BETA
