Question

How much energy will be spent in 15 minutes in a 5 KW electric heater.

Answer 1

Hint:We know about heating elements and filaments. When an electric current flows through the filament, the temperature of the filament rises since it is resistive, and the filaments become very hot and start glowing.

Complete step by step answer:
Given: The time for which the heater is operated is $t = 15\;\min $
The Power of the heater is $P = 5\;{\rm{kW}}$.
We know that to calculate the energy spent, we have to establish a relation between Power and energy. We can do it by the below-given formula,
$E = P\,t$
Here E is the energy spent.
Now we will substitute $t = 15\;\min $ $P = 5\;{\rm{kW}}$ in the above equation to find the value of energy spent. So after replacing, we will get the result as,
$E = \left( {5\;{\rm{kW}}} \right)\,\left( {15\;\min } \right)$
Now we will apply suitable conversions to get the energy in joules. Therefore,
$E = \left( {5\;{\rm{kW}} \times \dfrac{{1000\;{\rm{J/s}}}}{{1\;{\rm{kW}}}}} \right)\,\left( {15\;\min \, \times \,\dfrac{{60\;{\rm{s}}}}{{1\;\min }}} \right)\\
\therefore E = 4.5 \times {10^6}\;{\rm{J}}$

Therefore, the energy spent on the electric heater is $4.5 \times {10^6}\;{\rm{J}}$.

Additional information:
We must also be aware of that filaments are also used in incandescent lamps, and they're also the same thing happens that is the filaments are resistive, and when the current pass through the filaments, they get lighten up and starts glowing, and that is the effect what we receive as light energy from the bulbs.

Note:As we all know, heat is a low grade of energy, and work is high-grade energy. The point that is supplied to the heating is wasted 100 percent into the atmosphere. The heat that is generated inside the heater is lost to the atmosphere.