A) \[\frac{Mg-\pi IR{{B}_{0}}}{Mg+\pi IR{{B}_{0}}}\]
B) \[\frac{Mg+\pi IR{{B}_{0}}}{Mg-\pi IR{{B}_{0}}}\]
C) \[\frac{Mg-\left( {}^{IR{{B}_{0}}}/{}_{\pi } \right)}{Mg+\left( {}^{IR{{B}_{0}}}/{}_{\pi } \right)}\]
D) \[\frac{Mg+\left( {}^{IR{{B}_{0}}}/{}_{\pi } \right)}{Mg-\left( {}^{IR{{B}_{0}}}/{}_{\pi } \right)}\]
Correct Answer: B
Solution :
[b] Magnetic dipole moment \[\vec{\mu }=I.\pi {{R}^{2}}\hat{k}\] Magnetic torque \[{{\vec{\tau }}_{B}}=\vec{\mu }\times \vec{B}\] \[=I\pi {{R}^{2}}{{B}_{0}}(\hat{k}\times (-\hat{j}))=I\pi {{R}^{2}}{{B}_{0}}(\hat{i})\] To counterbalance this torque we must have \[{{T}_{1}}>{{T}_{2}}\]Torque about centre CYou need to login to perform this action.
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