Question

In a properly adjusted tangent galvanometer ,the deflection for 1 A current , is found to be $30^{\circ }$. Now the Coil is turned through $90^{\circ }$ about vertical axis, the deflection for , the same current will be

• A. 60${}^{\circ }$
• B. 30${}^{\circ }$
• C. 90${}^{\circ }$
• D. 0${}^{\circ }$

Answer 1

Answer: (D)

The basic concept used here is that force in the coil increases as its angle of twist increases as $F\propto$ $\theta$.
Now this force in the spring will be balanced by the force due to magnetic field.
Here the correct answer will be $0^{\circ }$ because in case of $90^{\circ }$ deflection when the current is passed there will be no more deflection since it is already been more that $30^0$.