Power Systems
Lightning arresters are used to protect electrical equipment against

 power frequency of over voltages.
  over voltages due to indirect lightning stroke.
 direct strokes of lightning.
 over currents due to lightning stroke.

ANSWER DOWNLOAD EXAMIANS APP

Power Systems
Gross head of an hydroelectric power station is

 the height of water level in the river where the tail race is provided.
 all of above.
 the height of water level in the river where the storage is provided.
  the difference of water level between the level in storage and tail race.

ANSWER DOWNLOAD EXAMIANS APP