Question

A substance of mass m kg requires a power input of P watts to remains in the molten state at its melting point. When the power is turned off, the sample completely solidifies in time t sec. What is the latent heat of fusion of the substance?

• A. $\frac{Pm}{t}$
• B. $\frac{Pt}{m}$
• C. $\frac{m}{Pt}$
• D. $\frac{t}{Pm}$

Answer 1

Answer: (B)

$\frac{Pt}{m}$

Answer 2

Heat lost in t sec = mL or heat lost per sec = $\frac{mL}{t}$. This must be the heat supplied for keeping the substance in molten state per sec.

\ $\frac{mL}{t}$=P or L = $\frac{Pt}{m}$