Lamps And Bulbs in Utilization Of Electrical Energy : Practice MCQ Questions & Answers with Explanations

Explanation: Sodium and Mercury Vapour Gas in Filament Lamps Definition: Sodium and mercury are two vapour gases commonly used in filament or discharge lamps due to their unique emission properties. These gases emit characteristic colors when excited by an electric current, making them suitable for various lighting applications. Sodium produces a yellow color, and mercury emits a green color when energized in such lamps.

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.