Question

The electrical energy in kilowatt hours consumed in operating ten $50W$ bulbs for $10hrs/day$ in a month of $30days$ is

• A. $1500$
• B. $15000$
• C. $15$
• D. $150$

Answer 1

Answer: (D)

$150$

Let

$n$ be the number of bulbs, $n=10$
$P$ be the power of each bulb, $P=50W$
total time to burn the bulb, $t=10\times 30=300hr$

Now the energy $E$, consumed in operating the bulbs is:
Energy consume by each built in 30 days $E=Pt=50\times 300$

Energy consume by 10 bulbs in 30 days $E=nPt=10\times 50\times 300Wh$

$E=150kWh$ (Option D)