Question

A tube light of 50 W is lighted for 4 hours and an electric bulb of 100 W is lighted for 3 hours. What will be the cost of consumed energy daily if cost per unit is ₹2?

• A. ₹ 4
• B. ₹ 1
• C. ₹ 15
• D. ₹ 3

Answer 1

The correct option is B ₹ 1

Electric power $=\frac{\text{Energy consumed}}{\text{Time taken}}\Rightarrow \text{Energy consumed}=\text{Electric power}\times \text{Time taken}\Rightarrow E=P\times t$

For tube light:

$P=50W=0.05kW(\because 1kilo={10}^3)t=4hE=0.05\times 4=0.2kWh=0.2unit(\because 1kWh=1unit)$

Thus, the tube light is using 0.2 unit.

For electric bulb:

$P=100W=0.1kWt=3hE=0.1\times 3=0.3kWh=0.3unit(\because 1kWh=1unit)$

Therefore, the electric bulb is using 0.3 unit.
Now, total units consumed $=0.2+0.3=0.5unit$

Cost of 1 unit = ₹2

$\therefore$ Cost of 0.5 unit $=0.5\times 2=₹1$

Hence, the correct answer is option (b).