Question

ask 1. In a 6kW boiler, 100 liters of water is heated. Measurements have shown that the water temperature has increased by 20 degrees Celsius within one hour. What is the usefulness of a boiler?

Solution: eta=78%

Task2. Immerse the electric heater in water of mass 5kg and temperature 15 degrees and connect it to a voltage of 220V. The heater is flowing with a current of 2A. What will be the temperature of the water after 15 minutes if we assume that the operation of electricity is entirely spent on heating the water?

Solution: t2=33,9 degrees

Task3. To measure the temperature in a furnace, we put in it an iron ball weighing 700g for a while. The ball is then thrown into a calorimeter containing 4.5 liters of water at 8.3 degrees. What is the temperature in the furnace if the final temperature in the calorimeter is 12.3 degrees?

Solution: t2=251,7 degrees

Task 4. During the preparation of tea, 6dl of 90 degree water was poured into an empty porcelain pan weighing 200g at 20 degrees. What is the final temperature of the tea if the specific heat capacity of the water is 4190JkgK ^ (- 1) and the porcelain is 840JkgK ^ (- 1)?

Solution: t=85,6 degrees

Please solvethis

Answer 1

Task 1

Power consumed = 6 kW

now Power delivered = Energy/time

Energy = = 100 X 4182 X20 = 8364000 J

time= 1 hour = 3600 sec

power delivered = 2.323 kW

Effeciency = 0.3872

Task 2

Power = VI =  220 X 2 = 440 W

now time = 15 minutes = 900 sec

Energy delivered = 440 X900 = 396000 J

this is used to heat the water so = 396000

T2 = 33.857 = 33.9

task 3

temp. of iron ball = temp. of Furnance = t

specific heat of iron = 460.548

now by calirometry

m2 =4.5 s2 = 4182    = 4

so t-12.3 = 239.498

t= 254.7

Task 4

m1 = 0.6 s1 =4182  

m2 = 0.2 s2 = 840

we get

T = 85.6