Electric Charges and Fields

Two types of electric charges

Positive and negative charges.

SI unit of electric charge

The coulomb (C).

Value of the elementary charge (e)

Approximately 1.6×10^-19 coulombs.

Conservation of charge principle

Total charge in an isolated system remains constant.

Processes for charging objects

Friction (triboelectric effect), conduction, and induction.

Conductors

Materials that allow charge to move freely.

Insulators

Materials that do not allow free movement of charge.

Semiconductors

Materials with properties between conductors and insulators.

Coulomb's Law

F=k(q1q2)/r^2, where k is Coulomb's constant.

Variation of electrostatic force with distance

Inversely proportional to the square of the distance.

Electric field

Region around a charged object where other charges experience a force.

Direction of electric field from a positive charge

Away from the charge.

Direction of electric field from a negative charge

Toward the charge.

Density of electric field lines

Represents the strength of the electric field.

Electric dipole

Two equal and opposite charges separated by a small distance.

Orientation of electric field of a dipole

Points from the positive to the negative charge.

Behavior of an electric dipole in a uniform electric field

Experiences a torque aligning it with the field.

Motion of a charged particle in a uniform electric field

Experiences constant force and acceleration, resulting in a parabolic trajectory.

Electric flux

Measure of the number of electric field lines passing through a surface.

Relation of electric flux to Gauss's Law

Gauss's Law relates electric flux through a closed surface to the enclosed charge.

Practical application of electric fields

Capacitors.

Experiment measuring the elementary charge

Millikan's oil drop experiment.

Coulomb's constant (k)

8.99×10^9 N⋅m^2/C^2.

Stage for Gauss's Law in electric fields study

Understanding electric flux and its relation to enclosed charge.