Along wire is known to have a radius greater than 4.0 mm and to carry a current uniformly distributed over its cross section. if the magnitude of the magnetic field is 0.285 mt at a point 4.0 mm from the axis of the wire and 0.200 mt at a point 10 mm from the axis, what is the radius of the wire?

It may seem strange that the selected velocity does not depend on either the mass or the charge of the particle. (for example, would the velocity of a neutral particle be selected by passage through this device? ) the explanation of this is that the mass and the charge control the resolution of the device--particles with the wrong velocity will be accelerated away from the straight line and will not pass through the exit slit. if the acceleration depends strongly on the velocity, then particles with just slightly wrong velocities will feel a substantial transverse acceleration and will not exit the selector. because the acc