Three resistors R1, R2 and R3 are connected one after another in a single conducting path forming a series circuit with a cell and a key.
(i) State the mathematical relation for the total resistance Req of these three resistors when they are connected in series.
(ii) Explain why the value of Req obtained in part (i) is always greater than the largest individual resistance among R1, R2 and R3.
(iii) A decorative lamp set uses three identical miniature bulbs each rated 1.5V,0.30A in series across a battery. Give a reason to justify why any one of these bulbs would burn out if it were connected alone across the same battery.