Three identical miniature lamps are each rated at 6V,3W. They are connected in series to a variable d.c. supply.
(i) From the rating, find the maximum safe current that may pass through one lamp.
(ii) Calculate the effective resistance of the three-lamp series string when each lamp operates at its rated conditions.
(iii) Determine the supply voltage required so that every lamp glows at its rated brightness when connected in this series arrangement.
(iv) If the supply voltage is accidentally increased so that the current becomes 1.5 times the rated current, compute the power dissipated in each lamp. Discuss briefly which lamp, if any, is likely to fuse first under these new conditions.