Question

What is the power rating of a heater that uses 1.2KWh of energy in 45minutes?

Answer 1

Explanations & Calculations

• If the power rating is P & the energy consumed in time t is E then,

$\qquad\qquad \begin{aligned} \small P &= \small Vi \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\text{and} \,\,\,\,\,\,\,\,\,\,\,\,\,E = Vit\\ \end{aligned}$

therefore,

$\qquad\qquad \begin{aligned} \small E &= \small Pt \cdots\cdots(1) \end{aligned}$

• kWh is a unit of energy (1kWh equals to $\small 1000W \times 3600s = 1000\times 3600 J$) & 45 minutes equals to $\frac{3}{4}h$. Therefore by (1),

$\qquad\qquad \begin{aligned} \small 1.2kWh &= \small P\times \frac{3}{4}h\\ \small P &= \small \bold{1.6kW =1600W} \end{aligned}$