1. một thùng thép nặng 80 kg chưa 250kg nước ở 150 °c .Cho vào thùng này 20 kg ước ở -10 °c .Tính nhiệt đọ cân bằng của hệ thống . 2. sau đó người ta nấu một lượng nước bằng bếp than có hiệu suất 40% rồi dẫn hơi nước ở 100°c vào thùng thép trên để có nhiệt độ của hệ thống là50°c
a) tính khối lượng hơi nước dã đưa vào bình
b) tính khối lượng than cần dùng, biết rằng nước để nấu có nhiệt độ ban đàu là 25°c , cnd = 2100j/kg. k , ct = 460j/kg. k, L =2,3.106 J/Kg. K ,λ= 3,4.105J/Kg. K,q =30.106/kg. k

In a steady-flow steam power plant system, two adiabatic high-pressure and low-pressure turbines ane used to generate power. superheated steam enters the high-pressure turbine at 8 mpa and 550°c. the steam expands in the high-pressure turbine to a saturated vapor at 3 mpa. in order to increase the powe generation of the power plant, another steam turbine working in a lower pressure ranges is deployed. the outlet vapor from the first turbine is heated up at a boiler to the temperature of 500 c at the constant pressure of first turbine's outlet (3 mpa). then, the vapor enters the second turbine and produces extra work. the exit conditions of the second turbine are 5o kpa and 90 percent quality. if the total power output of the power plant is 25 mw, determine a) the mass flow rate of the water (kg/s). b) heat transfer rate in the boiler (mw). (30 points) 3 mpa 00 c 8 mpa s0 c high pres turbine low pres boiler turbine 50 kpa 3 mpa 09 saturated vapor t heat engine, shown in the figure, operates between high temperature and low temperature of through a heat 4. a carnot tn and tu respectively. this heat engine receives energy from a heat reservoir at t exchanger where the heat transferred is proportional to the temperature difference as ? = k (z,-7, ). it rejects heat at a given low temperature tl. to design the heat engine for maximum work output, find the high temperature, th, as a function of tes and t. (15 points) qe

The magnetic field inside a superconducting solenoid is 4.50 t. the solenoid has an inner diameter of 6.20 cm and a length of 26.0 cm. determine (a) the magnetic energy density in the field and (b) the energy stored in the magnetic field within the solenoid.

If an atom contains 11 protons in its nucleus, predict the element with the atomic number and electronic configuration. will the number of electrons remain the same during the chemical reaction in such an atom? explain.