ELECTRICITY

Electrostatics

The study of stationary electric charges.

Electrodynamics

The study of electric charges in motion.

Electrification

can be created by contact, friction, or induction.

negative electric charge

Electrification is due to the movement of

electron

The smallest unit of electric charge is the

coulomb (C)

The fundamental unit of electric charge is

6.3x10^18

1 C =

1.6x10^-19 C/electron charge

What is the electrostatic charge of one electron?

Unlike charges attract; like charges repel.

Electrostatic Laws

Coulomb’s Law

The electrostatic force is directly proportional to the product of the electrostatic charges and inversely proportional to the square of the distance between them.

Coulomb’s Law Formula

Electric potential

is sometimes called voltage.

volt (V)

The unit of electric potential is the

Electric Current

• Flow of electrons in a conductor.

• Measured in amperes (A)

ampere

is proportional to the number of electrons flowing in the electric circuit.

One ampere

is equal to an electric charge of 1 C flowing through a conductor each second.

DC and AC

2 Types of Current

DC

• Electrons flowing only in one direction

AC

Electrons flowing alternately in opposite directions.

Electric Resistance

is measured in ohms (Ω)

Resistor

is a passive two terminal electrical component that implements electrical resistance as a circuit element.

electronics circuits

, resistors often used to limit current flow, to adjust signal levels, bias active elements, and terminate transmission lines among other uses.

Conductors

is any substance through which electrons flows easily.

Copper (Cu),

Aluminum (Al),

water

Conductors (3 examples)

Insulators

is any material that does not allow electron flow

Glass,

clay other earthlike material,

rubber

Insulators (3 examples)

semiconductor

is a material that under some conditions behave as an insulator and in other conditions behaves as a conductor.

William Shockley

demonstrated semiconduction

1946

William Shockley demonstrated semiconduction

Silicon (Si), germanium (Ge)

Semiconductors (2 examples)

Superconductivity

is the property of some materials to exhibit no resistance below a critical temperature (Tc).

1911

When were superconductors discovered?

1960s

When were superconductors commercially available in

Electric Circuits

When the resistance is controlled and the conductor is made into a closed path, the result is an electric current.

Ohm’s Law

The voltage across the total circuit or any portion of the circuit is equal to the current times the resistance.

series circuit

All circuit elements are connected in a line along the same conductor.

parallel circuit

Contains elements that are connected at their ends rather than lie in a line along a conductor.

1. The total resistance is equal to the sum of the individual resistances.

2. The current through each circuit elements is the same and is equal to the total circuit current.

3. The sum of the voltages across each circuit element is equal to the total circuit voltage.

Rules for Series Circuits

1. The sum of the currents through each circuit element is equal to the total circuit current.

2. The voltage across each circuit element is the same and is equal to the total circuit voltage.

3. The total resistance is the inverse of the sum of the reciprocals of each individual resistance.

Rules for Parallel Circuits

Electric Power

is measured in watts (W)

Electrical Fault

Is an electric power system, a fault or fault current is any abnormal electric current

ground fault (earth fault)

is any failure that allows unintended connection of power circuit conductors with the earth.

Electrical grounding

provides an alternate path for electricity to follow, rather than going through a person.

Electric Shock

happens when current passes through the body.

Electrocution

Refers to the injury or lethal dose of electrical energy

Electrical fires

may be caused by excessive resistance that generates heat

• Too much current running through wiring where overcurrent protection fails or does not exist • Faulty electrical outlets resulting in poor contact or arcing • Poor wiring connections and old wiring that is damaged and cannot support the load

Causes of Electrical fires

explosion

can occur when electricity ignites a flammable gas or combustible dust mixture in the air.

circuit breaker

is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by excess current from an overload or short circuit. Its basic function is to interrupt current flow after a fault is detected.