Question

An electric heater draws a current $4A$of and its element has a resistance of$40\Omega$. If the heater is switched on for $8$minutes, calculate the energy released in kilojoules.

Answer 1

We know that when an appliance is switched on, it gets heated. Thus the energy released is in the form of heat. We know that heat dissipated by an object is a function of current and resistance and the time taken. Thus, we can obtain the energy released.

Complete Step-By-Step Solution:
We know, in the question is given that the:
Resistance of the electric heater is $40\Omega$
Current drawn by it $4A$
We know that electrical heating is a process in which electrical energy is converted to heat energy. We know that, as the appliance draws current, it gets heated.
We know, heat dissipated is formulated as:
$H = {i^2}Rt$
Where,
$H$is the amount of heat dissipated
$i$ is the amount of current flowing through the appliance
$t$ is the time through which the appliance is heated.
The time given is in minutes, so we need to convert it in seconds.
Thus time becomes, $8 \times 60s = 240s$
Now, putting the values, we obtain:
Thus, we obtain:
$H = 16 \times 40 \times 240J = 153600J$
But, in the question, we need the answer in kilo-joules, therefore, dividing the obtained value by $1000$:
Therefore, we obtain:
$H = \dfrac{{153600}}{{1000}}KJ = 153.6KJ$
This is the required solution.

Note:
We often come across a similar term called power when we discuss heat and energy. Power is related to the energy dissipated. We define energy as the one that brings in the change and power is defined as the rate of change of energy.