Question

A heater gives heat at rate of 100W . It is used to heat 50g of water from 20degree celcius to 30 degree celcius . Specific heat of water is 4.2 J/g degree celcius . FIND the time taken to do so.​

Answer 1

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Answer 2

The time taken by the heater is 21s.

Given:

A heater gives heat at a rate of 100W. It is used to heat 50g of water from 20degree celsius to 30 degree Celsius. The specific heat of water is 4.2 J/g degree celsius.

To Find:

The time is taken.

Solution:

To find the time taken we will follow the following steps:

As we know,

The relation between heat and specific heat is:

$q = mc(tf - t0)$

Here, q is the heat

m is the specific heat

tf is the final temperature and t0 is the initial temperature.

Now,

In putting values we get,

$q = 50 \times 4.2 \times (30 - 20) = 50 \times 4.2 \times 10 = 2100 \: joule$

Now,

$power = \frac{ heat}{time}$

$time = \frac{q}{power} = \frac{2100}{100} = 21s$

Henceforth, the time taken by the heater is 21s.

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