Apower cycle operates between a lake’s surface water at a temperature of 300 k and water at a depth whose temperature is 285 k. at steady state the cycle develops a power output of 10 kw, while rejecting energy by heat transfer to the lower-temperature water at the rate 14,400 kj/min. determine (a) the thermal efficiency of the power cycle and (b) the maximum thermal efficiency for any such power cycle

a) Efficiency: 4%

b) Maximum thermal efficiency: 17%

Explanation:

First we calculate the total heat that come from the hot reservoir. This heat is the work output plus the rejected energy to the cold reservoir.

The efficienccy of the cycle can be calculated as the ratio between the work output and the heat input.

The maximum thermal efficiency of this cycle can be determined in function of the temperatures of the reservoirs by this equation:

answer: the correct answer is 1.

explanation: there are various process in which a radioactive nuclei decays:

1) alpha decay: in this process, a heavier nuclei decays into lighter nuclei by releasing alpha particle. the mass number is reduced by 4 units.

2) electron capture: in this decay process, a parent nuclei absorbs an electron and gets converted into a neutron. simply, a proton and an electron combines together to form a neutron. mass number does not change in this process.

3) gamma ray emission: it is a decay process in which an unstable nuclei gives excess energy by a spontaneous electromagnetic process. this decay releases . this process does not change the mass number.

4) positron emission: it is a type of decay process, in which a proton gets converted to neutron and an electron neutrino. this is also known as -decay. in this the mass number remains same.

from the above information, we see that only alpha-decay is producing a change in the mass number of the nucleus.

a.metals can become magnetic if they have many spinning electrons that create magnetic fields.d.only some metals are attracted by magnets; these metals are called ferromagnetic.

d.wrapping an insulated wire around a metal with ferromagnetic properties and applying an electric current.