when the number of turns in a coil is doubled without any change in the length of the circular coil

When the number of turns in a coil is doubled without any change in the length of the coil, its self-inductance becomes

When the number of turns in a toroidal coil is doubled, then the value of magnetic flux density will becomes-

Assertion : When number of turns in a coil is doubled, coefficient of self-inductance of the coil becomes 4 times. Reason : This is because L prop N^(2)

If number of turns in a coil is quadrupled, then self-inductance will be:

The self inductance of a coil is L . Keeping the length and area same, the number of turns in the coil is increased to four times. The self inductance of the coil will now be

If number of turns in the coil is increased, how will brightness change ?