ELECTRICITY by Rosanna Saprio

1)Electric current is defined as the rate at which charge flows through a surface (the cross section of a wire, for example).The SI unit for measuring an electric current is the ampere, which is the flow of electric charge across a surface at the rate of one coulomb per second. Electric current is measured using a device called an ammeter.The conventional symbol for current is I, used by André-Marie Ampère, after whom the unit of electric current is named,

r_saprio1 — 2017-11-25 15:09:06 UTC

2)In a conductive material, the moving charged particles which constitute the electric current are called charge carriers. In metals, which make up the wires and other conductors in most electrical circuits, the positively charged atomic nuclei are held in a fixed position, and the negatively charged electrons are free to move, carrying their charge from one place to another.Voltage, electric potential difference, electric pressure or electric tension is the difference in electric potential between two points per unit electric charge. The voltage between two points is equal to the work done per unit of charge against a static electric field to move the test charge between two points. This is measured in units of volts (a joule per coulomb).

r_saprio1 — 2017-11-25 15:18:18 UTC

An electric circuit is a path in which electrons from a voltage or current source flow.The point where those electrons enter an electrical circuit is called the "source" of electrons. The point where the electrons leave an electrical circuit is called the "return" or "earth ground". The exit point is called the "return" because electrons always end up at the source when they complete the path of an electrical circuit.

r_saprio1 — 2017-11-25 15:24:47 UTC

Circuits use two forms of electrical power: alternating current (AC) and direct current (DC).

Ohm's law

r_saprio1 — 2017-11-25 15:28:43 UTC

Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points. Introducing the constant of proportionality, the resistance ^] one arrives at the usual mathematical equation that describes this relationship
V= I*R

where I is the current through the conductor in units of amperes, V is the potential difference measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms. More specifically, Ohm's law states that the R in this relation is constant, independent of the current.

OHM'S SECOND LAW

luigi_cavallaro05 — 2017-12-02 09:23:35 UTC

Ohm discovered a second law which states that the resistance of a conductive wire is directly proportional to its length and inversely proportional to its transverse area. R(V) = p l
(A) A
where p is a constant of proportionality and is called resistivity. This depends on the material with which the wire is made and on its temperature. It is measured in ohms per meter. The two laws of Ohm are valid for most solid bodies and allow us to understand whether a material is a good insulator or a good conductor. The substances with intermediate characteristics are called semiconductors.
R=eletrical resistence
_{_/\/\/\/\_}=ohmmeter
L=length of the conduit
p=conduit material(rho)=resistivity

Conductors and insulators

simonacavallaro04 — 2017-12-02 15:01:03 UTC

Based on their electrical behavior, the materials are subdivided into conductors and insulators:
-Conductors: in them the electric charges can easily be neutralized in a short time,then let the electric current pass.All metals are conductive, for example, copper, silver, iron etc.
-Insulators: in them the electric charges move slowly and remain inside the body then they prevent the passage of electric current.Plastic materials are insulating,for example,wood, glass, air, paper.

ELECTRICAL CIRCUITS

antoniomainardi — 2017-12-02 16:54:18 UTC

The passage of electric current takes place in a closed process called an electric circuit.

It consists of a current generator, a conductor wire, a user and a switch.

An electric circuit is a closed path in which current flows because at its ends there is a potential difference. CIRCUIT OPEN: a circuit is open when the switch is lowered and then electric current circulates.

CIRCUIT CLOSED : a circuit is closed when the switch is raised and therefore no electrical current flows.
SERIES CIRCUIT: one circuit is called in series when the users are connected one after the other in such a way that only the first and the last are directly connected to the stack. PARALLEL CIRCUIT: a circuit is said in parallel when each user is connected in such a way that only the ends of the conductor are in common.

The electric circuit is formed by:

Generator
User
Thread
Switch