Question

Which uses more energy, a 250 W TV set in 1 hour or a 1200 W toaster in 10 minute?

Answer 1

Hint: We are given the power and time to use a TV and a toaster. To find which of them consumes more energy we need to find the energy consumed by both the appliances and compare them. To find the energy we have an equation relating energy, power and time. Thus we will get the solution.

Formula used:
$E=P\times t$

Complete answer:

In the question we are given the power and time used of two appliances; TV and a toaster.

Let ‘${{P}_{1}}$’ and ‘${{t}_{1}}$’ be the power and time used by the TV. Then we are given,

${{P}_{1}}=250W$ 

${{t}_{1}}=1hr$, by converting this time given in hour to minute, we will get

$\Rightarrow {{t}_{1}}=60\min =60\times 60=3600\,s$ 

Let ‘${{P}_{2}}$’ and ‘${{t}_{2}}$’ be the power and time used for of the toaster, then we have

${{P}_{2}}=1200W$ 

${{t}_{2}}=10\min =10 \times 60 = 600\,s$ 

In the question we are asked to find which of the two appliances uses more energy in the given time.

We know that the equation for energy is given as,

$E=P\times t$, where ‘E’ is the energy, ‘P’ is the power and ‘T’ is the time.

Therefore we will have the energy of the TV as,

$\Rightarrow {{E}_{1}}={{P}_{1}}\times {{t}_{1}}$ 

By substituting the values of power and time of the TV in the above equation, we will get

$\Rightarrow {{E}_{1}}=250\times 3600$ 

$\Rightarrow {{E}_{1}}=900000\,J$ 

Now let us calculate the energy of the toaster in 10 minutes. It can be calculated as,

$\Rightarrow {{E}_{2}}={{P}_{2}}\times {{t}_{2}}$ 

By giving the values for power and time of toaster in the above equation, we will get

$\Rightarrow {{E}_{2}}=1200\times 600$ 

$\Rightarrow {{E}_{2}}=720000\,J$ 

Thus we have the energy of the TV in 1 hour as 900000 Joules and the energy of the toaster in 10 minutes as 720000 Joules.

We know that $900000J>720000J$.

Therefore we can say that,

$\Rightarrow {{E}_{1}}>{{E}_{2}}$ 

That is, the energy consumed by the TV in 1 hour is more than the energy consumed by the toaster in 10 minutes.

Therefore the TV consumes more energy.

Note:

Energy can be simply defined as the capacity or ability to do a work. Energy is stored in a body as different forms like kinetic energy, potential energy, chemical energy, mechanical energy etc. it is not possible for us to create or destroy energy. We can only transfer energy from one form to another.