Electricity and Electric Circuits

• Electricity
• Presented by Dr. Miguel Angel Fitch Osuna

Electric Circuit Parts

• Generator
• Receptor (light bulb)
• Conductor
• Fuse
• Switch

Main Sources of Electrical Current

• Direct Current Voltage Source (DCVS)
• DC source provides constant voltages and flows without variation, can be stored in batteries, and is safer
• Direct Voltage (DV) allows use in multiple devices without needing a connection

Applications and Capacity of DC Voltage

• CD (direct current) voltages developed include:1.5V, 3V, 9V, 12V, 24V, 48V, and 96V
• Uses and applications include: toy cars, flashlights, cell phones, laptops, and automobiles

Alternating Current Voltage Source

• Electrical load variations in direction and time with periodic changes in voltage and current and are typically not constant

Alternating Current vs Direct Current

• Alternating current is a type where voltage value and direction alternate in a set time, and is able to transport large amounts of energy over long distances by using transformers.
• Alternating current can alternate between 50 and 60 cycles per second depending on the country and this is frequency
  • Alternating current waveform types include: sinusoidal, triangular, trapezoidal, etc, with sinusoidal being most common (used in homes and industry)
  • AC current exists in continuous and pulse form
• Direct current maintains a constant flow
  • It is not able to transport large amounts of energy, as it is thermodynamically inefficient, and cannot use transformers
• The frequency of direct current is zero because it remains constant
  • Exists in continuous and pulse form
  • Electronic circuits produce voltage pulses with time separation for application purposes

Control Units

• Control units or switches or dimmers allow or prevent the passage of electric current through an electric circuit

Protective Elements Used in Electrical Circuits - Fuses

• A fuse is a component that protects electrical and electronic circuits in any device or installation
  • Fuses in optimal conditions allow a current to pass
• A fuse is composed of a filament or metal sheet designed to burn and cut off the current flow
• If the current begins to increase for any reason, it will damage the electrical device if it enters the circuit with too high a value
  • Fuses are placed before the current enters the circuit

Thermal Magnetic Circuit Breakers

• Thermal magnetic switches (also known as circuit breakers) protect electrical network conductors and equipment by interrupting the energy flow when a short circuit or current overload occurs in the wiring
• The symbol used for the themomagnetic switch is a wavy line ending in a straight line

Main Types of Circuit Breakers

• Automatic or magneto-thermal switch:
• Used for short circuit failures or where there is an overload of the circuit, or values ​​greater than certain limits are detected

How a Thermal Magnetic Switch Works

• Based on the dilation of metal by heat and attractive forces generated by magnetic fields
• There is a bimetal strip that carries current and conducts electricity
  • As this increases, the metal begins to dissipate heat and dilate, causing it to open the circuit
  • There is a coil that carries a current and generates a certain magnetic field
  • As the current increases, the intensity of the magnetic field increases
  • A pulling force is generated in a nucleus which causes the core to be strongly attracted to the magnetic field
  • When the field is strong enough to attract the entire core (excessive electrical current), the circuit will cut

Differential Switch

• Compares current entering vs current exiting a circuit through magnetic fields that are produced
  • If fields are produced by the same intensity in opposing directions, they are cancelled
  • It intensity varies from one another, a magnetic field makes a knob move that cuts off the electrical circuit
• Differential switches serve to protect people when they are electrocuted (grounded)

Single Pole Simple Electrical Switch

• Single pole switches are electrical mechanisms that have 2 positions, on and off.
  • In one position they let current pass, and in the other they cut it off

Simple Bipolar Electrical Switch

• Dual switch works the same way that a single pole switch, but is can also be used in humid environments, such as the bathroom
• An bipolar swtich uses 2 cables to cut the current: phase and neutral

2-Way Electric Switch or Two-Way Switch

• Used to control a light from two different places
  • 2-way switches are needed for this operation
  • Very useful switch for large rooms, hallways, and staircases because the light can be switch on and off from different points

Capacitor

• A capacitor is an electrical component that acquires a determined charge when subjected to a potential difference.
• A capacitor's fundamental characteristic is capacity (C), which indicates the amount of electricity it can store
• The capacity of a capacitor depends on these variables:
  • Surface area of ​​the plates
  • Type of dielectric material it contains
  • Distance between the two conductive plates

Capacitor Use Cases

• The function of a capacitor is to store an energy charge that can be released quickly
• Capacitors are most efficient in mechanisms that demand a rapid energy boost, such as flashlight, starters, amplifiers, etc
• Capacitors level intermediate currents when electricity fluctuates a lot
• Capacitors generate delays in circuits that require them

Types of Capacitors

• Electrolytic capacitor:

  • Quickly releases large amounts of energy for high initial output on motors.
  • Polar capacitors do not function well with alternating currents, as reverse polarization of electrolyte and casing causes shorts and explosions

• Tantalum capacitor:

  • Uses tantalum as an anode, giving it an improved capacity per volume than an aluminum electrolytic capacitor.
  • Using tantalum makes the dielectric layer thin

• Polyester capacitor:

  • Having high power and fast response, these capacitors utilize thin layers of polyester as a dielectric and aluminum to form their structures and are used for connections and disconnections of direct current with low tolerance filtering with audios
  • Polyester capacitors' small size, high yield, and little potency make them better over paper capacitors

• Ceramic capacitor:

  • Ceramic capacitors use different types of ceramics as a dielectric and can be formed from a single layer or from stacked layers
  • Depending on ceramics properties, capacitors can function at different frequencies.
  • These have very few losses.

• Capacitors parallel or in series:

  • Capacitors in series are two or more capacitors connected to one line
  • The positive capacitor is attached to the negative capacitor of the following capacitor and shares current charge; however, parallel capacitors include more than 2 capacitors.
  • The terminals connect to the other capacitor and share the same tension

Electrical Values

• Basic values to define an electrical circuit: voltage, intensity and resistance.

Voltage (V)

• The magnitude that maintains differences between positive and negative charges between two points in a circuit
• When two points with a difference in charges are connected by a conductor, electrons form where there is a higher negative charge
• Current stops when both points match charges or the circuit is interrupted.

Intensity (I)

• Amount of electrons displaced per second through a conductor
• Represented by an parallel arrow above letter I
• Units are in Amperes (A)
• Charge of an electron is super small
• Basic load unit is the coulomb

Electromotive Force (EMF)

• Force that origins in the flow of electricity
  • The difference of potential between terminals
  • Basic Measurement units for potential are volts
  • The volt equals the work of one joule per coulomb

Direction of Electrons and Intensity in An Electrical Circuit

• Electricity is a display of electrons from the negative towards the conductor's positive
• It is convention to call it instead intensity to the displacement of electrons so the intensity goes from the positive extreme to negative extreme of conductor

Resistance (R)

• Electrical resistance is the magnitude that measures the impediment of a material when traversed by electrical current
• Resistance is represented by the letter R
• Resistance units are in Ohms (Ω)

Colors Values for Resistors with 4 Bands

• There is reference material on how to calculate resistance by code.

Factors Affecting a Conductor's Electrical Resistance

• Length: the greater the length, the greater the resistance
• Area or transverse section: increased area decreases resistance
• Material type of the conductor
• Temperature: heat increases resistance

Equation That That Allows Resistance Calculation From a Conductor

• ρ is resistivity of the material (copper resistivity is 0.0172)
• l = length of the cable in meters
• S = section of the conducting wire expressed in mm²

Ohm’s Law

• Math equation that relates voltage with intensity and resistance of an specific consume
• V = Voltage
• R = Resistance
• I = Current
• George Simon Ohm created theory

Calculating Power in an Electric Circuit

• Ability to perform the work on electric currents and electric potential
• Formula P= V · i = R ·i² = V²/R
• Power's unit of measurement: Watt
• W= J/Seg

Joule Effect

• When current cycles to a conductor, kinetic energy is converted to hear and elevates the temperature of the conductor
• Name comes from Joule
• Electro loads that use resistance lose electrical energy which is converted to heat
• This is called the joule effect - Heat from an electrical current on a conductor directly proportional to the square of current intensity, to resistance, and duration connected

Equations

• Q= 0.24 12Rt(electrical power product and time with consummation; energy converted to heat and constant)
• Equations in joules and constant representative of the equivalence: 1 joule of work = 0.24 calories of energy

Applications of Joule Effec

• Each of these devices uses electrical current in resistance
• Radiant elements convert Joule effect to high fusion temperature around 2500 with high temperature to emit heat

Another Application

• Fuse Construction apply Joule effect
• Fuse is used to limits the electrical current to low melt elements to fuse if to much current applies and overheat the circuit to an short