Electricity Basics: Fundamentals and Terms

Electrostatics

• Induction creates a temporary and opposite charge in another object without contact.
• Friction involves direct contact and rubbing.
• Conductors are materials that allow electrons to flow freely.
• Insulators are materials that hinder the flow of electrons.

Interaction Between Charged Objects

• Opposite charges attract, while like charges repel.
• The interaction between charged objects is a non-contact force that acts over some distance of separation.
• Coulomb's Law states that the magnitude of the electric force between two-point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance that separates them.

Electric Field

• An electric field is a region of space in which an electric charge will experience a force when placed in it.
• Electric fields can be produced by one or more charges.
• It is a vector quantity whose direction is that of the force on a positive charge.
• A positively charged particle creates an outward electric field, while a negatively charged particle creates an inward electric field.
• A neutrally charged particle does not produce an outward or inward electric field.

Electric Potential

• Electric potential energy is the energy needed to move an electric charge against an electric field.
• It is a conservative energy.
• Electric potential is defined as the amount of electric potential energy per unit charge.

Electric Potential Difference

• Electric potential difference is defined as the difference of electrical potential between two points.
• It is also known as voltage and has the unit volt (V).

Factors Affecting Electric Potential

• The amount of charge creating the potential affects the electric potential.
• The distance from the charge also affects the electric potential.

Capacitors and Dielectrics

• A capacitor has the ability or capacity to store energy.
• It consists of two plates of conducting material separated by an insulator.
• The amount of charge Q obtained by each plate is proportional to the magnitude of the potential difference V between them.

Capacitance

• Capacitance is expressed in coulombs per volt, or Farad (F).
• The capacitance C generally has no dependence on Q or V.
• The value of C depends primarily on the size, shape, and relative position of the conductive plates.

Dielectrics

• A dielectric is a material used to separate the conductive plates of a capacitor.
• It keeps the conducting plates from coming into contact, allowing for smaller plate separations and therefore higher capacitances.

Current, Resistance, and Electromotive Force

• Pressure (voltage) causes flow (current).
• Voltage is the potential difference in charge between two points in an electrical field.
• Current is the rate at which electric charge flows past a point in a circuit.

Ohm's Law

• There is a direct proportionality between current and voltage, but an inverse proportionality between current and resistance.

Resistance

• The property of a material that limits current flow.
• The SI unit for resistance is the Ohm (Ω).

Resistor

• Any device that contributes appreciable resistance to the flow of a charge.