Question

Rana uses a bulb of 220V -120W during his study of 5 hours daily.Rony uses a table lamp of 220V -120W for 6 hours daily. The event of each unit of electrical energy is 10 taka. Determine the total current of bulb & light used by rana & Roney?

Answer 1

Explanations & Calculations

Usage of Rana

• The current

$\qquad\qquad \begin{aligned} \small P&=\small Vi\to i= \small \frac{P}{V}=\frac{120W}{220V}\\ \small i&=\small 0.545A \end{aligned}$

• Number of units consumed

$\qquad\qquad \begin{aligned} \small U&=\small \frac{120}{1000}kW\times5hrs\\ &=\small 0.6\,kWh \end{aligned}$

• Cost of usage

$\qquad\qquad \begin{aligned} \small &=\small 0.6\times10=6\,taka \end{aligned}$

Usage of Rony

• The current

$\qquad\qquad \begin{aligned} \small i&&=\small 0.545A \end{aligned}$ (same as for Rana due to both lamps being the same)

• Units consumed

$\qquad\qquad \begin{aligned} \small U&=\small \frac{120}{1000}kW\times6hrs\\ &=\small 0.72\,kWh \end{aligned}$

• Cost of usage

$\qquad\qquad \begin{aligned} \small &=\small 0.72\times10=7.2\,taka \end{aligned}$

Total current consumption by both of them

$\qquad\qquad \begin{aligned} \small &=\small 2\times0.545A=1.09\,A \end{aligned}$

Total cost for the usage of both

$\qquad\qquad \begin{aligned} \small &=\small 6+7.2=13.2\,taka \end{aligned}$

$\qquad\qquad \begin{aligned} \small \end{aligned}$