Question

Let us assume that a 100W electric bulb is lighted for 2hr daily and four $40W$ are lighted for $4hr$ every day. Find out the energy consumed in $kWh$ in $30days$.

Answer 1

Hint: Energy required can be found by taking the product of the power consumed and the time taken. First of all find the energy consumed by a $100W$ bulb. In the same way, find the energy consumed by $40W$ bulb. Calculate the total energy consumed per day and calculate the same for $30days$. This will help you in answering this question.

Complete step by step solution:
The energy consumed can be found by taking the product of the power consumed and the time taken. This can be expressed as,
$E=P\cdot t$
Where $P$ be the power consumed and $t$ be the time taken.
The energy consumed by $100W$bulb for a day can be shown as,
$E=2\times 100Wh=0.2kWh$
The energy consumed by the $40W$bulb per day can be represented as,
$E=4\times 4\times 40Wh=0.64kWh$
The total energy consumed per day will be the sum of the energy consumed by the $100W$bulb for a day and energy consumed by the $40W$bulb per day. That is,
${{E}_{T}}=0.2+0.64kWh=0.84kWh$
Therefore the energy consumed in thirty days will be the product of the total energy consumed per day and the number of days. This can be written as,
${{E}_{T}}^{\prime }=30\times 0.84=25.2kWh$

The total energy consumed by the bulbs for thirty days will be $25.2kWh$.

Note:
Power is defined as the amount of energy that has been converted or transferred per unit time. The unit of the power is watt which is equivalent to one joule per second in the International System of Units. In ancient times, the power is often known as activity. Power is a scalar quantity which is having only magnitude.