A magnetic needle of magnetic moment 6.7 $$\times$$ 10^-2 A m² and moment of inertia 7.5 $$\times$$ 10^-6 kg m² is performing simple harmonic oscillations in a magnetic field of 0.01 T. Time taken for 10 complete oscillations is:

A fighter plane of length 20 m, wing span (distance from tip of one wing to the tip of the other wing) of 15 m and height 5 m is flying towards east over Delhi. Its speed is 240 ms⁻¹. The earth’s magnetic field over Delhi is 5 $$ \times $$10⁻⁵ T with the declination angle ~ 0^o and dip of $$\theta $$ such that sin $$\theta $$ = 2/3 . If the voltage developed is V_B between the lower and upper side of the plane and V_W between the tips of the wings then V_B and V_W are close to :

Hysteresis loops for two magnetic materials $$A$$ and $$B$$ are given below :

These materials are used to make magnets for electric generators, transformer core and electromagnet core. Then it is proper to use :

The coercivity of a small magnet where the ferromagnet gets demagnetized is $$3 \times {10^3}\,A{m^{ - 1}}.$$ The current required to be passed in a solenoid of length $$10$$ $$cm$$ and number of turns $$100,$$ so that the magnet gets demagnetized when inside the solenoid, is :