An electron is moving along the line of force in magnetic field B with velocity u, then the maximum force acting on the charge is given by _.

Explanation

The force acting on a charge moving through a magnetic field is given by the equation F = qVBsinθ, where q is the charge, B is the magnetic field, V is the velocity of the charge, and θ is the angle between the velocity vector and the magnetic field vector. In this case, the electron is moving along the line of force in the magnetic field B, which means that the angle between the velocity vector and the magnetic field vector is 0°. Therefore, sinθ = sin(0°) = 0. Substituting sinθ = 0 into the equation F = qVBsinθ, we get: F = qVB(0) = 0 This means that the force acting on the electron is zero, and hence the correct option is D.