Discharging Metals

Discharging Metals

1. Let's say a metal ball is in a container. The bottom of the container is a metal plate that is positively charged.

   • The top of the container is a metal lid which has been earthed.

2. 1. When the ball is at the bottom, on the plate, what will be its charge?

   • Positive.
   • This is because when the ball touches the positive plate, it gives it a positive charge too.

3. 2. What will happen next?

   • The ball will float up to the earthed lid at the top.
   • This is because like charges repel, so the positively charged plate will repel the now positively charged ball, meaning it will move up and away from the plate.

4. 3. What happens when the ball is at the top?

   • It will fall back down to the plate again.
   • This is because when the ball touches the earthed lid, it gives the ball electrons. These cancel out the protons (that make it a positively charged object) so the ball is now neutral, or uncharged.
     • Since it is now uncharged, there is nothing keeping it away from the plate at the bottom, so it falls down
     • If the ball had been negatively charged, the earthed lid would have taken away its electrons (that would make it negatively charged), meaning it would become neutral or uncharged.

5. 4. What happens now, when the ball is at the bottom again?

   • It will continue to move up and down between the metal plate and the earthed lid.
   • This is because it falls back down to the plate, which makes it positively charged, so it repels the plate, moving up again. However, when it is at the top, the earthed lid gives it electrons, making it neutral, so the ball falls back down again...
     • … and the process repeats again and again!