Question

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

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

Answer 1

The correct option is D $0^o$

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 $0^0$ because in case of ${90}^0$ deflection when the current is passed there will be no more deflection since it is already been more that ${30}^0$.