(a) Mutual Induction: Mutual Induction is a phenomenon which occurs when the current in a coil is changing, an e.m.f will be induced in a tear-by circuit due to some of the magnetic flux produced by the first circuit linking the second circuit. (b) The uses of electromagnets are in: - electric bells or telephone earpieces - generators or electric motors - industrial robots - separation of iron scraps from debris - electromagnetic switches or magnetic relays - cranes fbr lifting or transporting heavy magnetic materials - magnetic resonance scanners, i.e. in medical diagnosis. (i) The changing magnetic flux in X induces changing magnetic flux in Y which induces the current that light up the bulb. (ii) As the distance between X and Y decreases, the magnetic flux density linking coil Y increases, hence the induced e.m.f. increase hence the brightners of the lamp. (iii) The insulated soft iron wires increases the magnetic flux through coil Y, hence increase in the induced current in Y, therefore, the filament of the lamp glows brighter. (d) Total e,m,f. E = 2V Total internal resistance r \(\frac{1}{r} + \frac{1}{r_2} = \frac{1}{0.4} + \frac{1}{0.1}\) e = 0.08\(\Omega\) E = I(R + r) 2 = I(5 + 0.08) I = \(\frac{2}{5.08}\) = 0.394A