Electrostatics and Magnetism

Coulumb’s Law

F = kq1q2/r² in Newtons

electric field

E=Fe/q in N/C

electric field with Q

E = kQ/r² in N/C

positive point charge

moves in same direction as field

negative point charge

will move opposite direction of field

electric potential energy

U = q(change in V), = qEd in Joules

electric potential energy with Q

U = kQq/r in Joules

electric dipole moment

p = qd

electric potential

V = U/q in J/C, work required to move positive test charge from infinity to particular point

electric potential with Q

V = kQ/r

potential difference

change in V = W/q in J/C

oppositely charged plates separated

V = Ed

magnetic field long straight wire

B = uoI/2pir

magnetic field loop wire

B = uoI/2r

magnetic force point charge

Fb = qvBsin(theta)

centripetal force

Fc = mv²/r

magnetic force current carrying wire

Fb = ILBsin(theta)

magnet

field lines point S to N

electric potential near dipole

V = (kqd/r²)cos(theta)

torque on dipole

pEsin(theta)

E

electric field

B

magnetic field

V

electric potential

q

test charge

Q

source charge

protons charge

+1.6 × 10^-19 C

electrons charge

-1.6 × 10^-19 C

k in coulumb’s law

9 × 10^9 Nm² / C²

field lines protons

move away

field lines electrons

move towards

stronger field lines

further apart

charges and electric potential energy

want to reduce potential energy

field lines and electric potential

lines point from high potential to low potential

positive point charge and electric potential

move from high to low potentials

negative point charge and electric potential

move from low to high potentials

voltmeter

reads positive - negative

total electric potential

add potentials from each charge

right hand rule positive moving charge

thumb velocity, pointer finger magnetic field, middle finger magnetic force

right hand rule straight wire

thumb direction of current, curl fingers direction of field

right hand rule coiled wire

thumb magnetic field line, curl fingers is current