Electric Charges and Electric Fields
- Forces like gravity, magnetic, and electric forces are fundamental to our understanding of the structure of all matter.
- The amber effect – amber when rubbed could attract small bits of dried straw.
- Electrically Charged objects – any material that behaves like rubbed amber.
- Neutral charge – Materials that show no amber effect.
- During the Renaissance it was observed that electrified objects fall into 2 groups:
- When two pieces of the same material are rubbed by a third, they always repel.
- When each of the two pieces in in the previous point are rubbed by different materials, they either attract or repel each other, depending upon the 3rd material.
- Benjamin Franklin was first to name the 2 charged states
- positive charges
- negative charges
- Franklin thought that:
- Neutral objects have a normal amount of electric fluid.
- A positive object had an excess of fluid
- a negative object had too little fluid
- We have defined charge as follows:
- Negative charge – the charge that an ebonite rod acquires when rubbed with fur.
- any object repelled by the ebonite rod has a negative charge.
- any object attracted to the ebonite rod has a positive charge
e.g. glass rubbed with silk
- Law of electric charge – Opposite electric charges attract each other. Similar electric charges repel each other. Charged objects attract some neutral objects.
December 6, 2013