Two 1000 W electric heaters are connected in parallel to a 220 V supply protected by…
MATHEMATICS · Single correct · ISC · Physics · Current Electricity · Electrical energy and power
Problem
Two 1000 W electric heaters are connected in parallel to a 220 V supply protected by a 5 A fuse. Each heater works safely when used alone, but the fuse melts as soon as both are switched on together. Which condition best explains the blowing of the fuse?
(a) A short circuit between the live and neutral conductors has produced an almost zero‐resistance path, so the current instantly exceeds the 5 A rating.
(b) Both heaters simply draw more current than the 5 A fuse can carry, i.e.\ overloading of the circuit.
(c) Because the appliances are connected in parallel, the supply voltage effectively doubles to about 440 V, driving a current well above 5 A.
(d) The mains voltage dipped below its normal value; this reduced the filament resistance of the heaters and therefore made a very large current flow.