To solve this problem we apply the concepts related to the electric torque generated by the electromagnetic field. Mathematically this Torque can be written under the following relation

Here,
N = Number of Turns
I = Current
A = Area
B = Magnetic Field
The maximum torque will be reached when the angle is 90 degrees, then we will have the following relation,

Magnetic Field is given at function of the number of loops, permeability constant at free space at the perimeter, then



Replacing at the first equation we have,


Answer:
Magnetic field strength required for this is 0.25 T
Explanation:
As we know that the proton moves in circular path in uniform magnetic field
so the radius of the path of the circle is given as

here we know that




now we have

so we have

Acceleration of an object is depended upon the net force acting open the object and the mass of the object
Answer:
A. can never be efficient due to friction