Question

The rate of change of torque with deflection $\left(\frac{d\tau }{d\theta }\right)$ is maximum for a magnetic suspended freely in a uniform magnetic field when $\theta$ is

• A. ${90}^{\circ }$
• B. ${60}^{\circ }$
• C. ${45}^{\circ }$
• D. $0^{\circ }$

Answer 1

The correct option is D $0^{\circ }$

Torque experienced by the magnet is,

$\tau =MB\sin \theta$

$\frac{d\tau }{d\theta }=MB\cos \theta$

$\frac{d\tau }{d\theta }$ is maximum when $\cos \theta =1\Rightarrow \theta =0^{\circ }$

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Hence, $\left(D\right)$ is the correct answer.