Fundamentals of Electric Dipoles and Current

Electric dipole Two equal and opposite charges separated by a small distance.

Permanent electric dipole A permanent dipole has a constant separation of charges.

Induced electric dipole An induced dipole forms temporarily in response to an external electric field.

Good solvent property of water Because it has a permanent electric dipole that allows it to interact with and dissolve polar substances.

Dipole in a uniform electric field It experiences no net force but does experience a torque.

Electric current I = dQ/dt

the rate of flow of charge over time.

Conventional current A flow of positive charges (opposite to electron flow in metals).

Charge movement in a conductor An electric field.

Drift velocity The average velocity of charge carriers in a conductor.

Current density (J) Current per unit area: J = I/A.

Resistivity formula ρ = E/J.

Resistance formula R = ρL/A.

Ohm's Law V = IR.

Ohmic materials Ohmic materials have constant resistance.

Non-ohmic materials Non-ohmic materials do not obey Ohm's Law.

Electromotive force (EMF) Energy per unit charge provided by a source; not an actual force.

Terminal voltage calculation V_ab = ε - Ir.

Voltmeter connection In parallel.

Ammeter connection In series.

Power formulas for a resistor P = I²R

P = V²/R

Short circuit danger It can cause excessive current

leading to overheating or damage.

Kirchhoff's Junction Rule The total current into a junction equals the total current out: ∑I = 0.

Kirchhoff's Loop Rule The total voltage change around a closed loop is zero: ∑V = 0.

Sign convention for voltages in loops Positive when moving with potential drop or emf; negative when moving against.