Question

An electric bulb of $60W$ is used for $6hrs/day$. Calculate the units of energy consumed in one day by the bulb
A. 0.18units
B. 0.36 units
C. 0.54 units
D. 0.72 units

Answer 1

Hint:Energy is the capability of any object to do work while power obtained by any object or particle is the work done by the object or particle in a particular interval of time. The SI unit of power is Watt while the SI unit of energy is Joule. Though units of energy are given in terms of power as 1unit = 1 kWh.

Complete step by step answer:
Energy is the ability of a material to do work. Energy cannot be destroyed nor can it be created, it can only be transferred from one form into another. In our case, the electrical energy is converted into light energy. An electrical bulb is working for 6 hours. The power of the electric bulb is given to be 60 Watts. We can convert the power of electric bulb from Watt into kilowatt as follows:
\[ 1kW=1000W\\
\Rightarrow 60W = \dfrac{{60}}{{1000}}kW \\
\Rightarrow 60W = 0.06kW\]
We have converted the unit of power because of the fact that the unit of energy in terms of electrical units is given by 1units= 1kWh. The relation between power, energy and time is given as follows:
\[E = P \times t\]
Here, E is the energy of the bulb, P is the power dissipated by the bulb and t is the time during which the bulb was dissipating the power or the energy. Thus;
\[E=0.06 \times 6 \\
\Rightarrow E =0.36kWh \\
\therefore E = 0.36units\]

Hence, option B is the correct answer.

Note: We neglect that there is any form of leakage in energy produced by the 60Wattt bulb such as in the form of heat or in any other way and all the energy produced by the bulb is converted into light energy from electrical energy. However, there cannot be such ideal cases in real life and energy is dissipated in the form of heat.