A heater is used for 5 minutes to heat 500g of water from 20˚C to 50˚C. What is the power of the heater? (The specific heat capacity of water is 4.2 J/gC).
Correct answer: C. 210 W
- A. 1260 W
- B. 12.6 kW
- C. 210 W
- D. 12.6 W
Explanation
t= 5 min = 5*60 = 300 secm= 500 gΔT change in temperature = 50°C-20°C = 30°Cc= 4.2Q [heat supplied/energy] = mcΔT = 500*4.2*30 = 63,000 J Power P = energy/time = 63,000/300 P= 210 W
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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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