A school laboratory technician wishes to design individual fused plugs for two appliances that will sometimes be used together on a 230 V supply: a precision balance rated 115 W and a hot plate rated 1610 W.
(a) Calculate the current drawn by each appliance.
(b) The technician first considers protecting both appliances with a single 10 A fuse fitted in the common extension lead. Show, with calculations, why this arrangement fails to give adequate protection to one of the appliances.
(c) The technician decides to provide separate fuses inside each plug. Determine the lowest standard fuse rating that should be used for each plug, choosing from 2 A, 3 A, 5 A, 10 A, and justify your selections.
(d) Explain qualitatively how the use of separate fuses improves safety compared with the single-fuse arrangement, making specific reference to over-current protection for the balance.