Question

what problems will be caused if lights and fans are turned on while going out

Answer 1

 1)a huge amount of energy will  lose which cause exploitation of resourses
 2)  if the electrical appliances are are of poor quality then there is chance of fire or burning

Answer 2

firstly, the main problem is exploitation of our resources .once they are over they will take millions of years to form.so we should save our resources by saving electricity. 
second thing, if we are leaving the lights on then they burn out sooner.
so if we switch off the lights when not in use it can also make the lights stay longer.
third thing is that,if we leave the lights on this can led to shot circuits and fire.