The strength of the magnetic field in which the magnet of a vibration magnetometer is oscillating is increased $4$ times its original value. The frequency of oscillation would then become

Two magnets are held together in a vibration magnetometer and are allowed to oscillate in the earth’s magnetic field. With like poles of magnets together, $12\, oscillations$ per minute are made but for unlike poles together only $4\, oscillations$ per minute are executed. The ratio of their magnetic moments is

Twists of suspension fibre should be removed in vibration magnetometer so that

The number of turns and radius of cross-section of the coil of a tangent galvanometer are doubled. The reduction factor $K $ will be

Before using the tangent galvanometer, its coil is set in