Physics midterm one electric charge and Coulomb’s law

neutral atom

A neutral atom has the same number of protons as electrons.

positive ion

A positive ion is an atom with one or more electrons removed.

negative ion

A negative ion has gained one or more electrons.

Two positive or two negative charges …… each other.

repel

A positive

charge and a negative charge ……. each other.

attract

Note when an object for ex a rod gets rubbed to a carpet they would attract since each one would gain its own different charge when they were in contact

A …….. permits the

easy movement of charge

through it. An ……

does not. Ex:

conductor….insulator Most metals and humans

are good conductors, while

most nonmetals are

insulators.

….,…..are

intermediate in their

properties between good

conductors and good

insulators.

Semiconductors …..

Semiconductors are special materials that can act like both conductors and insulators, but it depends on certain conditions, like temperature or if they’re given energy.

• When there’s low energy (like at low temperatures), semiconductors act more like insulators—they don’t conduct electricity well.

• When there’s more energy (like when you heat them or apply an electric field), they act more like conductors—they let electricity flow better.

So, it’s not the material changing from conductor to insulator, but rather how it behaves under different conditions that makes it unique.

the negative rod is able to charge the metal ball

without losing any of its own charge. This process is called

charging by induction.

Imp note

Electric forces on uncharged objects

The charge within an insulator can shift slightly. As a result, a

charged object can exert electric forces on neutral objects

………. is particle of “zero” size carrying a charge, e.g.

electrons and protons.

Point charge

More precisely , particles’separation is much larger than

particle dimension.

Note to the note we mean that the distance between individual particles is much greater than the size of each particle itself.

We can have few charges separated by large distances, or

many charges spread like touching each other:

Which is called

Continuous Charge Distribution

………… The magnitude

of the electric force between two

point charges is directly proportional

to the product of their charges and

inversely proportional to the square of

the distance between them.

Coulomb’s law

Coulomb’s law Formula

F=k |q1.q2|/r2

k” is a constant called Coulomb constant

In empty space (Air) and in SI system The number is

9×10^9 Nm²/c²

……………………….When two

charges exert forces simultaneously on a third

charge, the total force acting on that charge is the

vector sum of the forces that the two charges would

exert individually.

Principle of superposition of forces: ….. vector sum is the process of combining those forces to find the total effect of an object

Rules to set the equilibrium position point where the net

electrostatic force is zero:

1- if the two charges are like charges the position of equilibrium will

be between them and close to the small charge in magnitude.

2- if the two charges are unlike charge, the equilibrium position will

be out of the charges and close to the small one in magnitude

Vector has both

Magnitude and direction

Ke is also written as

1/4pieE0 or instead of E0 ke

The constant E0is called the…….

and it equals……

permittivity of free space. 8.85×10^-12

Fe and fg are both

Inverse square forces An inverse-square law means that the force gets weaker as the distance increases, specifically decreasing by the square of the distance (so if the distance doubles, the force becomes four times weaker).

The elementary charge e number is….

1.6×10^-19c