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A 100W heater is used melt 50g ice at 0°C. How long should the heater be switched on? (The specific latent heat of fusion of ice is 334 J/g)

Correct answer: C. 2.8 minutes

  • A. 28 minutes
  • B. 16.7 minutes
  • C. 2.8 minutes
  • D. 167 minutes

Explanation

Q = mLf; where Q is the heat supplied, m is mass of ice, and Lf is the specific latent heat of fusion of ice. So Q = 50 x 334 = 16,700 JPower = Energy/TimeTherefore, Time = E/P = 16700 / 100 = 167 seconds which is equal to 2.8 minutes. Hence, Option C is correct.

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About Thermal Equilibrium and Heat

Thermal equilibrium means that bodies in contact have the same temperature and no net heat flows between them. The topic distinguishes heat from temperature, uses the zeroth law of thermodynamics, and covers heat transfer, specific heat capacity, thermal expansion and the conditions for reaching equilibrium.

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