Page 8 - GALIET PHYSICS BLOSSOMS III

(1) Electromagnetism
(i) Imagine you want to explain to someone who has not attended this class, how electromagnetism works. You need to begin by explaining some of the facts. We consider first static phenomena.
Explain first what would be seen in an experiment where we have a small metal ball, which has been charged up with positive charge using a nylon rod. Explain how it is charged, and then what happens when you bring other “test charges” near to it. Show how one can then find Coulomb’s results. Draw a picture of the force field one finds from the metal ball. How do you think you would you measure these forces?
Charging the Metal Ball by Induction
(Induction occurs when electric charges are induced at a distance, without contact between the objects)
1. We can charge the nylon rod negatively by friction when we rub the rod with a material or substance that has less electron affinity.
2. We bring the negatively charged and partly insulated rod close to the neutral metal ball, which sits on an insulated stand to avoid charges passing unto the earth.
3. Free electrons are repelled to the opposite side of the sphere. The side closest to the rod will become positively charged.
4. We then ground the ball on the side that has the electron charge, and the electrons will be removed from the conducting metal ball.
5. We remove the grounding from the metal ball.
6. When the metal ball is ungrounded, there are more protons than electrons on the ball. As protons
take over and are distributed everywhere, the metal ball becomes positively charged.
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