question_answer

Two concentric coils each of radius equal to 2\[mg(h-d)-\frac{1}{2}k{{d}^{2}}\] cm are placed at right angles to each other. 3 A and 4 A are the currents flowing in each coil respectively. The magnetic induction in \[Wb/{{m}^{2}}\] at the centre of the coils will be \[({{\mu }_{0}}=4\pi \,\times {{10}^{-7}}\,Wb/Am)\]

A)  \[12\times {{10}^{-5}}\]                              

B)  \[{{10}^{-5}}\]

C)  \[5\times {{10}^{-5}}\]                 

D)        \[7\times {{10}^{-5}}\]

Correct Answer: C

Solution :

\[\Rightarrow \] \[V=\frac{av}{A}\] \[p+\rho gh+\frac{1}{2}\rho {{v}^{2}}=p+0+\frac{1}{2}\rho {{v}^{2}}\] \[\Rightarrow \] \[{{v}^{2}}=\frac{2gh}{1-{{\left( \frac{a}{A} \right)}^{2}}}=\frac{2\times 10\times (3-0.525)}{1-{{(0.1)}^{2}}}\]   \[=50{{(m/s)}^{2}}\] \[U=k|x{{|}^{3}}\] \[\Rightarrow \]