Question

A 30 watt immersion heater just keeps 600 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

The heat supplied by the heater while the metal changes state is Q = Pt.

Time = 6 × 60 = 360 s

Q = 30 × 360 = 10800 J

Using Q = mL

$$L = \frac{Q}{m}$$

$$= \frac{10800}{600}$$

= 18 Jg⁻¹