Answer:
B'=1.935 T
Step-by-step explanation:
Given that
magnetic field ,B= 0.645 T
We know that magnetic filed in the solenoid is given as
![B=\mu _0 n\ I](https://img.qammunity.org/2021/formulas/physics/college/s714muqpbkq1w7zi8gbsa39im8quggbp5f.png)
I=Current
n=Number of turn per unit length
μ0 =magnetic permeability
Now when the current increased by 3 factors
I'=3 I
Then the magnetic filed
![B'=\mu _0 n\ I'](https://img.qammunity.org/2021/formulas/physics/college/9sfe475sub65f1810jq65eohih61812q3x.png)
![B'=\mu _0 n\ (3I)](https://img.qammunity.org/2021/formulas/physics/college/kytyqrgmddoolzlsez8hufju61w7m7xo82.png)
B'=3 B
That is why
B' = 3 x 0.645 T
B'=1.935 T
Therefore the new magnetic filed will be 1.935 T.