Question

The formula ${\text{E = Pt}}$ gives the energy, ${\text{E}}$ watt hours, used when an electrical appliance of power ${\text{P}}$ watts is used for ${\text{t}}$ hours. What is the energy used in this situation: A. $1400 {\text{W}}$ blow dryer is used for ${\text{10 min}}$ ?

Answer 1

Hint: The relation between energy and power with time is given in the question. To find the required answer of energy we have to put values in the given formula. Energy is the ability to do any work. In the given question energy is used by electrical appliances.

Complete step by step answer:
Here in the question Energy is in watt and given by the formula:
${\text{E = Pt}}\,\,\,\,......{\text{(i)}}$ ,
Here, ${\text{P}}$ is power of the appliance and ${\text{t}}$ is the time in hours for which the appliance is in use,
Given in the question,
${\text{P = 1400 W}}$ ,
${\text{t = 10 min = }}\dfrac{1}{6}{\text{ hours}}$
Now putting the given values in the equation $({\text{i)}}$ , we get,
${\text{E = 1400 }} \times {\text{ }}\dfrac{1}{6}$
On solving this we get,
$ \Rightarrow {\text{E = 233}}{\text{.333 Whr}}$
Hence the required answer is ${\text{E = 233}}{\text{.333 Whr}}$.

Note: Power is energy consumed per unit given time. In physics, power is the amount of energy transferred or converted from one form to another per unit time. In the given question, electrical energy is consumed by the electrical appliance. Here consumed means that conversion of energy from one form to another. Also the law of conservation of energy tells us that energy can’t be created nor destroyed, but can change from one form to another.