WAEC Physics 2021 Paper

Concept:Electrical power is the product of current and voltage, and the energy consumed is power multiplied by time.Explanation:The bulb draws a current of $I = 2.0\,\mathrm{A}$ from a supply of $V = 440\,\mathrm{V}$.So, the power is $P = IV = 2.0 \times 440 = 880\,\mathrm{W}$.Two days in hours is $t = 2 \times 24 = 48\,\mathrm{h}$.Energy consumed is $E = P \times t = 880 \times 48 = 42{,}240\,\mathrm{Wh}$.This equals $42.24\,\mathrm{kWh}$, since $1000\,\mathrm{Wh} = 1\,\mathrm{kWh}$.At $\$0.40$ per kilowatt-hour, the total cost is $42.24 \times 0.40 = \$16.896$.Rounded to two decimal places, the cost is $\$16.90$.Answer:\$$16.90$ (Option A)