Concept The total power consumed in the circuit is given by: P = V × I where, P = Power V = Voltage I = Current Calculation Given, Mains voltage = 230 V Lamps are 100 W each and behave as resistive loads (power factor ≈ 1) The circuit is protected by a 5 A fuse. For continuous loads, you should limit continuous current to 80% of the fuse rating (common safety practice/derating for continuous service) Allowed continuous current = 5 A × 0.8 = 4 A Current per lamp = ${100\space W\over 230\space V}=0.4348 \space A$ Number of lamps = ${4\space A\over 0.4348\space A}= 9$ So maximum = 9 lamps of 100 W each.