Questions

Muhammad had to leave Mecca his birth place where he started preaching and take refuse in Medina, where he was given a warm welcome. This event took place in AD 622 and is known as the year of the Hijira, or migration, which became the first year of the Muslim Calendar.

It returns -1

Dust particles such as coal dust(smoke) are fine particle of a solid (carbon in the case of smoke) dispersed in air. They are colloidal systems and the particles are charged either positive or negative. In an applied electrical field, they are attracted towards the opposite electrodes. Movement of the particles towards the electrodes is known as 'electrophoresis'. Hence electrophoresis is applied to remove smoke within the chimeny itself without allowing it to escape into the air and cause nuisance.