Question

a microwave oven is rated at 900 w. it is set to work at full power how long would it take to heat 270 g of milk from 10°C to 37°C

Answer 1

Given:

A microwave oven is rated at 900 watt.

To find:

Time taken to heat 270 g of milk from 10°C to 37°C ?

Calculation:

The basic principle in microwave is that:

• The energy provided by the microwave will be utilised to to change the temperature of the food being warmed inside the microwave.

Specific Heat capacity of milk = 3.93 kJ/(Kg K)

According to Principles of Calorimetry:

$\therefore \: energy = mc\Delta \theta$

$\implies \: power \times time = mc\Delta \theta$

$\implies \:900\times time = 0.270(3930)(37 - 10)$

$\implies \:900\times time = 0.270(3930)(27)$

$\implies \:90\times time = 0.270(393)(27)$

$\implies \:10\times time = 0.27(393)(3)$

$\implies \: time = 0.27(39.3)(3)$

$\implies \: time = 31.83 \: sec$

So, time required is 31.83 secs.