The purpose of interpoles in DC machines is to nullify

interpoles is widely use to improve commutation
place between main poles fitted to yoke
functions:
to neutralize armature mmf in commutating zone
to produce some flux in commutating zone

DC series motors are best suited for traction work because

Torque in d.c motor = k* φ * Ia
In series motor φ α Ia
Tα I²
N α 1/φ
N α 1/T

If the voltage at the two ends of a line are 132 kV, and its reactance is 40 Ω, the stability limit of the line is

The purpose of providing a choke in a tube light is

Which lightning stroke is most dangerous?

Distribution transformers have good all day efficiency due to

all day efficiency is ratio of energy output to the energy input taken over 24 hour period.
design distribution transformer for max. efficiency occurring at the avarage output power.
performance of distribution transformer represent by all day efficiency.