When the number of turns in a coil are made 3 times without any change in the length of the coil, its self inductance becomes

Two solenoids of equal number of turns have their lengths as well as radii in the same ratio $1: 3$. The ratio of their self inductance will be

If number of turns per unit length in a solenoid is tripled, the self inductance of solenoid will

The number of turns in the primary of a transformer are 1000 and in secondary 3000. If 80 V a.c. is applied to the primary, the potential difference per turn of the secondary coil is