Question

A house is fitted with seven tubelights of rating 220 V, 40 W each, two bulbs of rating 220 V, 60 W each, five fans each drawing a current of 0.4 A at 220 V, and a heater of resistance 48.4 $\Omega$. The main line power supplied to the house is at 220 V. Calculate the bill for the month of January if tubelights and bulbs are used for 6 h daily, fans for 1 h daily, and heater for 10 h daily. The electricity is to cost ₹2 per unit.

Answer 1

₹796.08

Answer 2

1. Calculate the power of each appliance:

   • Tubelights: $7 \times 40 \text{ W} = 280 \text{ W}$
   • Bulbs: $2 \times 60 \text{ W} = 120 \text{ W}$
   • Fans: $5 \times (220 \text{ V} \times 0.4 \text{ A}) = 5 \times 88 \text{ W} = 440 \text{ W}$
   • Heater: $\frac{(220 \text{ V})^2}{48.4 \Omega} = \frac{48400}{48.4} \text{ W} = 1000 \text{ W}$

2. Calculate daily energy consumption (in kWh):

   • Tubelights: $\frac{280 \text{ W} \times 6 \text{ h}}{1000} = 1.68 \text{ kWh}$
   • Bulbs: $\frac{120 \text{ W} \times 6 \text{ h}}{1000} = 0.72 \text{ kWh}$
   • Fans: $\frac{440 \text{ W} \times 1 \text{ h}}{1000} = 0.44 \text{ kWh}$
   • Heater: $\frac{1000 \text{ W} \times 10 \text{ h}}{1000} = 10 \text{ kWh}$

3. Total daily energy consumption:

   • $1.68 \text{ kWh} + 0.72 \text{ kWh} + 0.44 \text{ kWh} + 10 \text{ kWh} = 12.84 \text{ kWh}$

4. Total monthly energy consumption (January = 31 days):

   • $12.84 \text{ kWh/day} \times 31 \text{ days} = 398.04 \text{ kWh}$

5. Total electricity bill:

   • $398.04 \text{ kWh} \times ₹2/\text{kWh} = ₹796.08$