In a classroom demonstration, a light aluminium rod AB of length 0.20m is hung horizontally by thin threads so that it is free to move. A current of 6A is sent through the rod from end A to end B using a battery and connecting wires. A pair of flat pole pieces of an electromagnet produce a uniform magnetic field of 0.4T in the region of the rod such that the field lines are horizontal and point from West to East.
a. (i) Draw a neat labelled diagram of the arrangement showing the directions of current, magnetic field, and the expected force on the rod.
b. (ii) Calculate the magnitude of the force acting on the rod.
c. (iii) Explain qualitatively why the rod swings in the direction obtained in part (i).
d. (iv) Suggest any two changes in the experimental set-up (other than changing the magnetic field strength) that would increase the magnitude of the force, and justify how each change achieves this.