At certain place a magnet makes 30 oscillations per minute. At another place if the magnetic induction is increased by two times the magnetic induction at first place, then the time period of same magnet will be

In the hysteresis curve the value of magnetization (B) which will be present in a substance when value of magnetizing force $$(\mathrm{H})$$ is made zero $$(\mathrm{H}=0)$$ is called as

Magnetic shielding is done by surrounding the instrument to be protected from magnetic field by

For which of the following substances, the magnetic susceptibility is independent of temperature?