1. Electrostatics Chapter 32

2. Electrical forces arise from particles in atoms Electrons are attracted to protons. This holds electrons in orbits around the nucleus of an atom Opposite charges attract Like charges repel All electrons are identical Atoms usually have as many electrons as protons, so the atom has a net charge of zero. An ion is produced when an atom gains or loses an electron An atom with more positive charge than negative charge is called a cation An atom with more negative charge than positive charge is called an anion

4. Electrical vs Gravitational Force Which is stronger? Electrical or Gravitational force? It turns out that Electrical force is 1 x 10 36 times stronger than gravitational force! 1,000,000,000,000,000,000,000,000,000,000,000,000 Newtons law of gravitation states that the force of gravity between two objects is proportional to their mass. We feel a strong pull on us due to Earth’s gravity, but this is because the mass of the Earth is very large compared to us. F G = G m 1 m 2 d 2

5. Coulomb’s Law When an atom becomes positively or negatively charged, there is a transfer of electrons Conservation of Charge states that at all levels macroscopic or microscopic, electric charge is neither created or destroyed. Electric force between two objects operates similar manner

6. The coulomb is the SI unit of charge 1 coulomb (C) = 6.24 x 10 18 electrons (q) k = Coulomb’s Law Constant (9 x 10 9 N*m 2 /C 2 ) d = distance between charges q 1 q 2 d 2 F = k

7. Materials through which electrons are able to move easily are called good conductors of electricity Examples of good conductors: silver copper gold aluminum iron steel Materials that resist the flow of electrons through them are called good insulators of electricity Examples of good insulators rubber wood glass styrofoam Conductors vs Insulators

8. Friction vs Induction Electrons can be transferred from one surface to another by friction “If the object is a good conductor, the charge will spread to all parts of its surface because the like charges repel each other” - Hewitt p. 509

9. Lightning in thunderstorms is produced by friction between water droplets and/or hail within a cloud. Lightning can also be produced by friction between ash particles in volcanic eruptions (above). http://www.supertightstuff.com/02/02/pictures/tight-pictures/volcanoes-and-lightning/

10. Electrons can move in a conducting surface when a charge object is moved close to it. This can occur even without contact between the two surfaces. A charge is said to be induced in the spheres. (see above)