Question

A $30$ watt immersion heater just keeps $600\mathrm{g}$ of molten metal at its melting point. The heater is switched off and the temperature starts falling after $6\min$. Calculate sp. latent heat of fusion of the metal.

Answer 1

Step 1: Given data

Power of immersion heater is $P=30W$.

Mass of the molten metal is $M=600g$.

Temperature starts falling after $t=6min=6\times 60=360s$.

Step 2: Finding the heat energy furnished by the heater

Heat energy is $Q=P\times t$.

Substituting the known values,

$Q=30\times 360=10800J$

Step 3: Finding the specific latent heat of fusion of the metal ($L$)

$ML=Q$

Putting the known values,

$$\begin{gathered} 600\times L=10800 \\ L=\frac{10800}{600} \\ L=18J{g}^{-1} \end{gathered}$$

Hence, the specific latent heat of fusion of the metal is $18J{g}^{-1}$.