It considered as Zero Gage pressure.
Answer:
The minimum no. of turns is 
Explanation:
Given:
Magnetic field
T
Frequency
Hz
Area of turn

Voltage
V
From the formula of induced emf,

Where
and 
So number of turn is,



Therefore, the minimum no. of turns is 
Answer:
There is pressure on both the in and outsides of the balloon: high inside and low outside, respectively. In terms of air mass, high pressure has greater activity and tends to move upward (balloon rises); whereas low presssure, being slower, descends (balloon descends).
Explanation: