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Electricity

Introduction

Section titled “Introduction”

Electricity

Section titled “Electricity”

Electricity is the set of physical phenomena associated with the presence and flow of electric charge. It is a form of energy that comes in positive and negative forms, that occur naturally (as in lightning), or is produced (as in a generator).

Electric Circuit

Section titled “Electric Circuit”

An electric circuit is a closed path in which electrons from a voltage or current source flow. The electrons flow from the negative side of the voltage source, through the circuit, and back to the positive side of the voltage source.

A node is a point in the circuit where three or more circuit elements are connected.

Node Law
I1=I2+I3I_1 = I_2 + I_3

Measurement

Section titled “Measurement”

Voltage

Section titled “Voltage”

Voltage is the difference in electric potential between two points. It is the force that pushes the electric current through a circuit. It is measured in Volts (V).

We use the volmeter in parallel to measure the voltage.

Voltage Measurement

Current

Section titled “Current”

Current is the flow of electric charge. It is measured in Amperes (A).

We use the ammeter (ampere meter) in series to measure the current.

Current Measurement

Electrical Dipoles

Section titled “Electrical Dipoles”

Definition

Section titled “Definition”

A dipole is a portion of a circuit between two terminals (dipole).

Characteristics of a Dipole

Section titled “Characteristics of a Dipole”

It is the graphical representation of the relationship between the current ii (passing through the dipole) and the voltage uu (at its terminals).

Linear DipoleNon-linear Dipole
straight linenon-straight line
Linear Dipole
Non-linear Dipole

Generator Dipole vs Receptor Dipole

Section titled “Generator Dipole vs Receptor Dipole”
Generator DipoleReceptor Dipole
A dipole is a generator when it supplies energy to the circuit it is connected to.
The current exits from the positive side.
The arrows representing voltage and current are in the same direction.		A dipole is a receptor when it consumes energy.
The positive side of the dipole is the one through which the current enters.
The arrows representing voltage and current are in opposite directions.
Generator Dipole
Receptor Dipole

The Four Quadrants of a characteristic

Section titled “The Four Quadrants of a characteristic”
U>0,I<0U > 0, I < 0
Generator Dipole		U>0,I>0U > 0, I > 0
Receptor Dipole
U<0,I<0U < 0, I < 0
Receptor Dipole		U<0,I>0U < 0, I > 0
Generator Dipole

Common Passive Dipole

Section titled “Common Passive Dipole”
  • Resistor
  • Inductance
  • Capacitor

Electrical Circuits in Direct Current (DC)

Section titled “Electrical Circuits in Direct Current (DC)”

The current is the same at all points in the circuit

Equivalent Electrical Diagram of Passive Elements

Section titled “Equivalent Electrical Diagram of Passive Elements”
ElementIn direct current
Resistor Resistor IEEE
U=RIU = RI Resistor IEEE
Inductance Inductance
A cable Capacitor
Capacitor Capacitor
An open circuit Capacitor

Links to Resources

Section titled “Links to Resources”