A laboratory electromagnet is constructed by winding a closely packed solenoid over a 25cm long soft-iron rod of circular cross-section. The solenoid has 1500 turns.
a. (i) Calculate the magnetic field at the centre of the rod when a current of 2.0A flows through the winding. Assume the rod is absent (air core).
b. (ii) The soft-iron rod of relative permeability μr=1200 is now in place while the same current flows. Find the new magnitude of the magnetic field.
c. (iii) Keeping the rod in position, determine the current required to obtain a magnetic field of 1.5T at the centre.