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Question
A solid metal weighing 150 g melts at its melting point of 800 °C by providing heat at the rate of 100 W. The time taken for it to completely melt at the same temperature is 4 min. What is the specific latent heat of fusion of the metal?
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Solution
Given:
m = 150g = 150 × 10(-3) kg = 0.15 kg
Power (P) = 100W,
Time (t) = 4 min = 4 × 60 sec
The amount of heat supplied in 4 min
Heat energy (Q) = 100 × 4 × 60 = 24000 J
This heat energy is used in melting.
Let L be the latent specific heat.
∴ L = `"Q"/"m"`
∴ L = `24000/0.15`
= 1.6 × 105 J kg-1
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