ch 18 static electricity

Not included: Miliken's oil drop process

Like charges

repel

Opposite charges

attract

Why are static charges more noticeable in dry days?

There’s no water/moisture to connect with the charges

Ions

atoms that have gained or lost electrons and therefore have a charge

Charges cannot be…

created or destroyed, only transferred

A charged object’s charge is always…

Quantized - a multiple of fundamental charge

Charge of a proton

Fundamental charge but positive

Electric conductor

materials that allow charges to flow easily through them (most metals)

What makes electric conductors conductors?

The atoms are lined up neatly so electrons can smoothly travel

Electric insulator

materials that do not allow charges to flow through them (glass, plastic, rubber, silk)

semiconductors

Normally insulators but adding specific atoms as impurities can turn them into conductors (silicon, germanium)

superconductors

zero electrical resistance when below a certain temperature - can conduct electricity without heating up

Charging by contact

Rubbing two materials together - tho one who rubs electrons off the other is positive and whatever’s getting rubbed is negative. Both insulators and conductors can be charged like this

Grounding

conductor connected to the earth by wire or pipe

Induction

A neutral conductor is brought near another charged object then the conductor is grounded, no touching. Only conductors can be charged like this

How would a surface charge be induced on an insulator

polarization

The closer the charge makes more

repulsion or attraction

Coulomb’s law only applies to

point charges or particles and spherical distribution of charges

field force

force between two objects not in contact with eachother

which is stronger, electric or gravitational force?

electric

electric field (E) (N/C)

area around a charge where the charge can be “felt” by another object

How are electic field lines drawn?

positive to negative

Test charge

detects the presence of an electric field. Always positive.

Direction of the field

the direction of the force on the positive test charge

Electric potential (Ue) (J)

a static charge/ charge at rest. No potential

Electric potential difference (V)(V)

the work required to move a positive test charge between two points in an electric field

J/C =

1 V

Forces a electric field exerts on a test charge will always be…

parallel, is yes potential difference

Points along a circle are said to be

perpendicular, so that it moves in a circle and there will be no electric potential difference

Capacitor

stores charges, usually parallel plates seperateed by dielectric materials