Answer:
I = 21.94 A
Step-by-step explanation:
Given that
B= 0.15 T
Number of turns N= 3100
Length L = 57 cm
Diameter ,d= 7 cm
We know that magnetic field in the solenoid given as


Now by putting the values

I = 21.94 A
Therefore current need to produce 0.15 T magnetic filed is 21.94 A.