A 100 W heater is used to heat 500 g of water from 20˚C to 50˚C. How long should the heater be switched on? (The specific heat capacity of water is 4.2 J/gC).
Correct answer: C. 630 seconds
- A. 63 seconds
- B. 63 minutes
- C. 630 seconds
- D. 6.3 minutes.
Explanation
For specific heat capacity, use the formula Q = mcΔT.Heat required = (500)(4.2)(50-20).E = 63000J.Power is the amount of energy transferred or converted per unit time.Power = energy / time.100 = 63000/time.time = 6300/100.time = "630 seconds".
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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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