116 120

 116. What is the difference between earth resistance and earth electrode resistance?

Only one of the terminals is evident in the earth resistance. In order to find the

second terminal we should recourse to its definition: 

Earth Resistance is the resistance existing between the electrically accessible part of a buried electrode and another point of the earth, which is far away. The resistance of the electrode has the following

components :

( A) The resistance of the metal and that of the connection to it. 

(B) The contact resistance of the surrounding earth to the Electrode.

117. Which power plant has high load factor?

All base load power plants have a high load factor. If we use high efficiency power plants to supply the base load, we can reduce the cost of generation. Hydro power plants have a higher

efficiency than thermal & nuclear power plants.

118. Why an ac solenoid valve attract the plunger even though we interchanges the terminal?Will the poles changes?

Yes because the poles changes for every half-cycle of ac voltage so the polarity of AC voltage is continuously changing for every half cycle. 

So, interchanging of terminals in ac system does not show any difference. 

That's why the ac solenoid attract the plunger even though it's terminals are interchanged.

119. Define IDMT relay?

It is an inverse definite minimum time relay. In IDMT relay its operating is inversely proportional and also a characteristic of minimum time after which this relay operates. 

It is inverse in the sense, the tripping time will decrease as the magnitude of fault current increase.

120. What are the transformer losses?

TRANSFORMER LOSSES - Transformer losses have two sources-copper loss and magnetic

loss. Copper losses are caused by the resistance of the wire (I2R).Magnetic losses are caused by

eddy currents and hysteresis in the core. Copper loss is a constant after the coil has been wound

and therefore a measurable loss. Hysteresis is loss is constant for a particular voltage and current.

Eddy-current loss, however, is different for each frequency passed through the transformer.