1) electric field

Coulomb's law; E field (+definition) of 1) point charge 2) multiple point charges 3) long straight wire ; induced charges; field lines

Coulomb’s law (in vaccuum)

what happens to mutual forces between q1 and q2 when other charges are present?

no influence

E units

[V/m] or [N/C]

define electric field

force applied by a given charge on a positive unit charge at a specific position produced by the given charge at that position

force on a charge q in an electric field E

electric field of one point charge q1: give the force, E field magnitude

add small test charge q (+) close to q1
=> E decreases with 1/r²

=> force on a charge q in this E field: F=qE

electric field of multiple point charges

1) superposition: E = E1 + E2

=> force on a charge q: F=qE

electric field of long straight charged wire

1) trig; only x-components remain
=> E decreases with 1/x = 1/r² and is perpendicular to wire

how to induce charges (hint: Faraday cage)

bring conductor in electric field produced by 2 charged plates:

inside conductor: Etot = Eext + Eint = 0

why does Etot inside conductor for inducing charges = 0?

free charges inside conductor keep moving til equilibrium

give 4 characteristics shown by field lines

1 - E is always tan to field line

2 - E has same direction as field line

3 - field line density ~ magnitude (=strength) of field

4 - field lines never cross