An electrically heated tank contains 200 kg of water at 50oC with a cold water at 10oC entering the tank at the rate of 0. 2 kg/s and the hot water at 50oC leaving the tank at the same rate; the system is at the steady state. Suddenly the electric power input to the tank was cut off. Calculate the time it would take for the temperature of water in the tank to drop to 30oC. Assume that the specific heat of water is constant at 4. 2 kJ kg-1 K -1.

The space within which a test north pole experiences a force magnetic poles 2. a powerful stream of electrons flowing high above the earth in the ionosphere electrojet 3. a concept to explain the directional nature of a magnetic field field lines 4. coil of wire designed to produce a magnetic field by a current passing through its windings ionosphere 5. that region above the earth's atmosphere where particles exist in an ionized state magnetic field 6. the extremities of a magnet where the field lines tend to converge or concentrate aurora borealis 7. a phenomenon that occurs in the northern latitudes; the northern lights solenoid