Static Electricity

Charges

Positive and Negative

Static charges more on..

Dry days, due to their not being any moisture in the air to connect the charges

Convention

Rubbing hair with a balloon causes the balloon to become negatively charges and your hair is now positively charged

Ions

Atoms that have gained or loss electrons and have a charge

Negative Electrons

Move easily, due to protons being too fixed/stuck inside the atom.

Charges can only be…

transferred, never created or destroyed

Miliken’s Oil Drop Experiment

Oil droplets that were charged by ionization and moved between two plates. Gravity pulled them down, until he turned on the top (positive) plate, and the negative droplets attracted to that. ETC.

→ A charged object is always a multiple of a single electron called the Fundamental

Charge of an Electron

-1.60 × 10^-19 C and positive for a proton

Gaining/Losing an Electron

If you gain an electron in an object, then the charge is Negative

If you lose an electron in an object, the charge is positive

Charge: q

Conductors

Materials that allow charge to flow easily through them (like metals)

Insulators

Materials that don’t allow charge to easily go through them (glass, plastic, rubber, silk)

Semi-conductors

Insulators, but adding a specific atom can turn them into conductors (silicon, germanium)

Superconductors

Zero electrical resistance when below a specific temperature, can make electricity without heating up.

Conduction

Rubbing two things together, and making an object positive

• Charges insulators and conductors

Grounding

A conductor connected to earth by a copper pipe or a wire.

Induction

A neutral conductor that is brought near another charged object, but the conductor is grounded.

• NO TOUCHING

Polarization

Separation of a charge within an atom.

• A surface charge can be put on insulators through this, and the shift inside can make it act like charged object.

• Total charge is zero, no electrons lost or gained.

• PROXIMITY

Coulomb’s Law

The closer two charges are the greater repulsion/attraction there is, think magnets!

• Only applies to point charges (particles and circle distribution of charges)

• F = Kq1q2 / r² EVERYTHING HAS ABSOLUTE VALUE, ALL POSITIVE

• K = 9 × 10^9

Electric Field

Area around a charge that can be felt

• drawn from Positive to Negative

Test Charges

Detect the presence of an electric field AND ARE POSITIVE.

• N/C

• E - KQ / r² - Q is field’s charge

• Direction of the field is direction of force on the test charge.

• Make sure to add at the end.

• nC = ___ x 10^-9

Static Charges

Charges at rest that have Potential Energy

Electric Potential Energy

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

• ∆V - Volts

• J/C = 1 volt

• ∆V = -ED (E is field intensity w/ N/C, and D is direction)

Potential Difference ( moving of PE)

A test charge needs to move up, down, or parallel to make a difference.

EX: Test charge that moves in a circle around a charge has no difference because the distance stays the same -→ Zero Volts.

Capacitors

Used to store charge.

• Parallel plates separated by dielectric material (conductors)

Ratio of that stored charge to EP difference is Capacitance

• C = Q/ ∆V

• Farad (F)

• 1 F = 1 C/V

• 1F = — x 10^-6 if given in m/F

• Keyboard/camera flashes

• No field strength, use ∆V = KQ / R with absolute value