A teacher conducts a lesson for students in the light of kerosene lamps and a candle during a power-cut inside a house in Kolkata J

A teacher (C, top) conducts a lesson for students in the light of kerosene lamps and a candle during a power-cut inside a house in Kolkata July 31, 2012. Hundreds of millions of people across India were left without power on Tuesday in one of the world’s worst blackouts, trapping miners, stranding train travellers and plunging hospitals into darkness when grids collapsed for the second time in two days. REUTERS/Rupak De Chowdhuri (INDIA – Tags: ENERGY SOCIETY EDUCATION)