With the aid of diagrams, explain clearly what happens to the rotational speed of the ferromagnetic disc under the magnetic flux (B).

A particle of mass m, charge q and position x moves in a constant, uniform magnetic field B which points in a horizontal direction. The particle is also under the influence of gravity, g , acting vertically downwards. Write down the equation of motion and show that it is invariant under translations x -> x + x0. Obtain x = \alpha x \times n + gt + a where \alpha = qB/m, n is a unit vector in the direction of B and a is a constant vector. Show that, with a suitable choice of origin, a can be written in the form a = an. By choosing suitable axes, show that the particle undergoes a helical motion with a constant horizontal drift. Suppose that you now wish to eliminate the drift by imposing a uniform electric field E. Determine the direction and magnitude of E. Training

Suppose 3 straight, indefinitely long wires (with negligible radius) spaced in an equidistant fashion, each carrying a current I in the same radius. Calculate the location(s) in space, where the magnetic field drops to zero.

In the figure, a conducting rectangular body of dimensions d, = 6.28 m., d, = 3.98 m. and d, = 1.37 m moves at constant velocity V %3D (23.5 m/s)i through a uniform magnetic fieldB =(45.2 mT)j. (a) What is the resulting electric field within the body, in unit-vector notation? (b) What is the resulting potential difference across the body? %3D