Lecture 2 Flashcards
(10 cards)
What is an electrical ground?
A connection to the Earth, which is so big that an almost infinite number of electrons can be transferred to or from
it (usually through damp soil which is a conductor since there are dissolved ions)
What happens to a conductor when it is connected to the earth
It becomes grounded
Charging a conductor:
What happens when an object with net negative charge (e.g. rod or balloon) touches a neutral metal sphere
- some electrons can move onto it and give it a net negative charge
- extra electrons would not be attracted to the metal atoms since each atom already has an equal number of electrons and protons
- Since electrons repel and can easily move through a metal conductor, they will move as far apart from each other as possible and thus be distributed across the surface of the sphere
What happens if extra charges are transferred to an insulator
they are not able to move and distribute across the object
Charging by induction (without contact):
If a rod with net negative charge is brought near a neutral conducting sphere
- many of the existing electrons in the sphere
could be pushed to one side. - If a grounding wire was connected from that side to the Earth, some electrons could be pushed off the sphere into the Earth.
- If the wire is then disconnected, the sphere would have a net positive charge
Coulomb did measurements with —— charged spheres
uniformly
True or False For Coulomb’s law equation i is NOT right to assume this equation is valid for any two objects #1 and #2 having net charges q1 and q2
.
True
- NOT valid if the two objects are not spheres, or if they do not have the net (excess) charge uniformly distributed (even if the are spheres)
What are “Point charges” or “point particles”:
very tiny particles that for practical purposes can be assumed to have zero size, for example electrons
Formula to find Fx and Fy components
Fx = F cos
Fy = F sin
what is ^r 12
Is a “unit vector” (magnitude=1) pointing from #1 to #2
