Re: light switch won't turn off
This is a pretty common failure scenario for snap switches. One of the pivot points on the contact blade wears or breaks. This allows the contact blade to shift to the side and the actuator on the switch then contacts the return spring causing the friction you mentioned and the contact blade is only slightly moved from the stationary contact thus sparking. The switch is not reparable and will need to be replaced. do not use the switch any more the arcing is a fire hazard.
Be sure you live your life, because you are a long time dead.-Scottish Proverb