If the magnetic field at a distance r from a long straight current-carrying conductor is B, what will be the magnitude of the magnetic field at a distance 4r from the same conductor, assuming the current remains constant?

A straight conductor of length 1 m carrying a current of 5 A is placed perpendicular to a magnetic field of 0.2 T. The force acting on the conductor is ______.

The magnetic field at a point P situated at perpendicular distance 'R' from a long straight wire carrying a current of 12 A is 3 × 10-5 Wb/m2. The value of 'R' in mm is: (μ0 = 4π × 10-7 Wb/A·m)