Find the quantity of heat needed to melt 100g of ice at -10 °C
into water at 10 °C. (39900 J)
(Note: Specific heat of ice is
2100 Jkg 'K', specific heat
of water is 4200 Jkg K',
Latent heat of fusion of ice is
336000 Jkg ').

Approximately (assuming that the melting point of ice is .)

Explanation:

Convert the unit of mass to kilograms, so as to match the unit of the specific heat capacity of ice and of water.

The energy required comes in three parts:

The following equation gives the amount of energy required to raise the temperature of a sample of mass and specific heat capacity by :

,

where

For the first part of energy input, whereas . Calculate the change in the temperature:

.

Calculate the energy required to achieve that temperature change:

.

Similarly, for the third part of energy input, whereas . Calculate the change in the temperature:

.

Calculate the energy required to achieve that temperature change:

.

The second part of energy input requires a different equation. The energy required to melt a sample of mass and latent heat of fusion is:

.

Apply this equation to find the size of the second part of energy input:

.

Find the sum of these three parts of energy:

.

12000j is work done

5 w for 1hr = 5x60x60 joules=300x60=3000x6=18,000j as total energy conversion. efficiency of bulb needed for radiant to thermal within 18000