Electricity

Introduction

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

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.

I_1 = I_2 + I_3

Measurement

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.

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.

Electrical Dipoles

Definition

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

Characteristics of a Dipole

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

Linear Dipole	Non-linear Dipole
straight line	non-straight line

Generator Dipole vs Receptor Dipole

Generator Dipole	Receptor 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.