Physics 3 -(Test 1 Study Guide Chapters 21-24)

Streamlines and Electric Field Lines analogy:

A streamline is a line or curve whose tangent at any point is in the direction of the velocity of the fluid at that point.

principle of conservation of charge

The algebraic sum of all the electric charges in any closed system is constant.

Coulomb's Law

The magnitude of the electric force between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.

How to show if E(Electric field) is weaker or stronger at a point?

Where E is strong, we draw lines bunched closely together; where E is weaker, they are farther apart.

The direction of the electric field at any point is what?

tangent to the field line through that point.

The proton and neutron are combinations of other entities called what?

quarks, which have charges of plus and minus 1/3 and plus and minus 2/3 times the electron charge.

test charge

Any charge whose magnitude is very small, in fact negligible, as compared to that of the point charge, and which does not affect the electric field of the point charge, whose magnitude is to be found out, is called test charge. A test charge is an object (usually a point particle) that has negligible charge; one can ignore the electrical field generated by the object itself.

When a piece of paper is placed in contact with the drum and then what happens?

the toner particles stick to the paper and form an image.

When a force F acts on a particle that moves from point a to point b , the work done given by the force is what?

( a line integral) formula on page 755 (23.1)

The word "electric" is derived from the Greek word what?

elektron, meaning amber.

electric dipole

is a pair of point charges with equal magnitude and opposite sign (a positive charge q and a negative charge -q ) separated by a distance d

conductor

object or type of material that allows the flow of charge ( electrical current) in one or more directions.

point charges

charged bodies that are very small in comparison with the distance r between them, Coulomb found that the electric force is proportional to 1/r^2

Surrounding the nucleus are the what?

electrons, extending out to distances of the order of 10^-10 m from the nucleus

These experiments and many others like them have shown that there are what?

exactly two kinds of electric charge: the kind on the plastic rod rubbed with fur and the kind on the glass rod rubbed with silk.

Electric Field Line

is an imaginary line or curve drawn through a region of space so that its tangent at any point is in the direction of the electric-field vector at that point.

Benjamin Franklin (1706-1790) suggested calling these two kinds of charge what?

negative and positive, respectively, and these names are still used.

Today we say that the amber has acquired a what?

net electric charge, or has become charged

At any particular point, the electric field has a unique direction, so what will happen?

only one field line can pass through each point of the field. In other words, field lines never intersect.

The printer's light-sensitive imaging drum is given a positive charge. As the drum rotates, a laser beam shines on what?

selected areas of the drum, leaving those areas with a negative charge.

The protons and neutrons are held within stable atomic nuclei by an attractive interaction, called the what?

strong nuclear force, that overcomes the electric repulsion of the protons.

One way to think about this force is as an "action-at-a- distance" force which is what?

that is, as a force that acts across empty space without needing any matter (such as a push rod or a rope) to transmit it through the intervening space. (Gravity can also be thought of as an "action-at-a-distance" force.)

Isolated quarks have not been observed, and there are theoretical reasons to believe what?

that it is impossible in principle to observe a quark in isolation.

Gauss's law states what?

that the total electric flux through any closed surface (a surface enclosing a definite volume) is proportional to the total (net) electric charge inside the surface.

The ancient Greeks discovered as early as 600 B.C. that after they rubbed amber with wool what will happen?

the amber could attract other objects.

Positively charged particles of toner adhere only to what?

the areas of the drum "written" by the laser.

The negatively charged electrons are held within the atom by the what?

the attractive electric forces exerted on them by the positively charged nucleus.

The English scientist Michael Faraday (1791-1867) first introduced what?

the concept of field lines. He called them "lines of force," but the term "field lines" is preferable.

Electric field lines show what? E is a boldface letter with an arrow above it symbolizing that it is a vector

the direction of E at each point, and their spacing gives a general idea of the magnitude of E at each point.

Charles Augustin de Coulomb (1736-1806) studied what?

the interaction forces of charged particles in detail in 1784.

Plastic rods and fur (real or fake) are particularly good for demonstrating electrostatics which is what?

the interactions between electric charges that are at rest (or nearly so).

The protons and neutrons in an atom make up a small, very dense core called what?

the nucleus, with dimensions of the order of 10^-15 m.

Electric field lines can be a big help for what?

visualizing electric fields and making them seem more real.

When you scuff your shoes across a nylon carpet what will happen?

you become electrically charged, and you can charge a comb by passing it through dry hair.