An electron, moving in a uniform magnetic field, moves in a circle path perpendicular to the field lines and takes time 2t for each circle. if the electron's speed is tripled, what would now be its new period in terms of t?

Electromagnetic induction. a coil of wire contains n turns and has an electrical resistance r. the radius of each turn is a. initially, inside the coil there exists a uniform magnetic field of magnitude b0 parallel to the axis of the coil. the magnetic field is then reduced slowly. the current induced in the coil is i. how long does it take for the magnitude of the uniform field to drop to zero?