Electricity and magnetism are separate yet interconnected phenomena. Which of the following options does BEST support the idea that electricity and magnetism are interconnected? (A) Electricity is the phenomenon of electric charges, whether they are stopped or moving.
(B) When a particle is stationary or stopped, it has an electric field, yet if the charge is moving, it also generates a magnetic field.
{C) Any magnetic particle or object has a "north" and "south" pole, with the directions based on the orientation of the Earth's magnetic field.
(D) Magnetism, like electricity, also has associated units of measurement, such as Tesla (T).

As part of an industrial process, air as an ideal gas at 10 bar, 400k expands at steady state through a valve to a pressure of 4 bar. the mass flow rate of air is 0.5 kg/s. the air then passes through a heat exchanger where it is cooled to a temperature of 295k with negligible change in pressure. the valve can be modeled as a throttling process, and kinetic and potential energy effects can be neglected. (a) for a control volume enclosing the valve and heat exchanger and enough of the local surroundings that the heat transfer occurs at the ambient temperature of 295 k, determine the rate of entropy production, in kw/k. (b) if the expansion valve were replaced by an adiabatic turbine operating isentropically, what would be the entropy production? compare the results of parts (a) and (b) and discuss.