Gopal Jadhav

In one complete cycle of refrigeration, the refrigerant, a liquid such as fluorinated hydrocarbon, goes through the following steps. The refrigerant in the closed tube passes through the nozzle and expands, into a low pressure area. This adiabatic expansion results in reduction in pressure and temperature of the fluid and the fluid turns into a gas. The cold gas is in thermal contact with the inner compartment of the fridge. Here it absorbs heat at constant pressure from the contents of the fridge. The gas passes to a compressor where it does work in adiabatic compression. This raises it's temperature and converts it back into a liquid. The hot liquid passes through the coils on the outside of the refrigerator and releases heat to the air outside in an isobaric compression process. The compressor, driven by an external source of energy, does work on the refrigerant during each cycle.

The colour of the light i.e. it's wavelength, emitted by an LED depends on the compound semiconductor material used and it's composition ( and doping levels. ) 

The current that does not lead to power consumption is called wattless current. In the case of a purely inductive circuit or a purely capacitive circuit, average power consumed over a complete cycle is zero and hence the corresponding alternating current in the circuit is called wattless current.

A hydraulic lift is a machine consisting of two oil-filled cylinders hydraulically connected. It is used for lifting a heavy object by applying a small force on the oil which transmits the pressure.

A heat engine is a device which takes a system through a repeated thermodynamic cycle that converts part of the heat supplied by a hot reservoir into work ( mechanical energy ) and releases the remaining part to a cold reservoir.At the end of every cycle, the system is returned to the initial state.

Resistance is opposition to flow of charges (current) and appears in a DC Circuit as well as in an AC circuit. In a purely resistive circuit, current and voltage are always in phase. When reactance is not zero.there is nonzero phase difference between current and voltage. Resistance does not depend on the frequency of AC unless the frequency is very high.     Reactance depends on the frequency of AC. In case of an inductor, reactance increases linearly with frequency. In case of a capacitor, reactance decreases as frequency of AC increases; it is inversely proportional to frequency. Resistance gives rise to production of joule heat in a component.ln a circuit with pure reactance, there is no production of heat.