Introduction to Electricity, Schemes and Mind Maps of Electronics

Download Introduction to Electricity and more Schemes and Mind Maps Electronics in PDF only on Docsity! INTRODUCTION TO ELECTRICITY 1-4 Comparison of AC and DC Electricity Under the principles of AC electricity. Power is the product of voltage and Current. Watts = Volts x Amperes Under the principle of AC electricity, the product of volts and amperes is equal to the quantity called volt-ampere (v.a.) which is not the same as watts. Thus; Volt Amperes = Volts x Amperes And to convert volt-ampere to watts or power, a power fac- tor (pf) is introduced. And to get power in an AC circuit, we have the following formula: Watts Volts x Amperes x power factor W = V * I * pf ILLUSTRATION 1-1 A 12 amperes electric fan and blower with a power factor of 0.85 was connected to a 240 volts convenient outlet (c.o). Calculate the current and power in the circuit. SOLUTION Power (watts) = Volts x Amperes x power factor W = 240 v. x 12 amp. x 0.85 W2,448 watts ILLUSTRATION 1-2 An electric motor has a trade mark label of 2 horse power, 240 volts, 15 amperes. Calculate the motor power factor. INTRODUCTION TO ELECTRICITY The Input side is classified as the Primary while the Out- put side is classified as the Secondary. Under this condition, the transformer is said to be 120/240 volts step up transformer with 120 primary and 240 volts secondary. The same transformer could be used as step down trans- former by reversing the supply and the load The 240 volts will be the primary and the 120 volt the secondary. In short, trans- formers are reversible. 1-8 Power and Energy Power and Energy is too frequently interchangeably used. Power is the technical term for the common word work, and Work, is the product of Power and Time expressed in the following equation: Energy or Work Power x Time What is Power? - Power is the rate at which energy is used or alternatively, the rate at which work is done. Since energy and power is synonymous, power implies continuity. That is, the use of energy at particular rate over a given span of time. The concept of power involves time at the rate at which work is done. Thus, multiplying power by time gives energy. What is Energy? In electrical terms, energy is synonymous with Fuel. It is associated with work. Energy can be ex- pressed in gallons, liters. barrels or tons of oil, coal, kilowatt hour or consumed electricity and cost of operations. In technical terms, Energy is expressed in units of BTU (calories), foot pound (joules) or kilowatt hour. Under the English Unit System, the unit of power is ex- pressed in horse power, BTU per hour, watt and kilowatt. Un- der the Metric System or SI, it is correspondingly expressed as joules per second, serious thought, considering the advantages of the 240 volts over the 120 volts circuit. The Advantages of using 240 volts over the 120 volts current supply are: INTRODUCTION TO ELECTRICUTY Voltage drop in wire = Carried current x Resistance of wire The power loss in the wire conductor can be calculated as the product of the voltage and the current. It is equal to the components resistance times the current squared. P = I x (I x R); P = I2R The power loss in the conductor wire is transformed into heat. Comparatively, a 1200 watts appliance rating has 10 amperes current flow on a 120 volts current supply compared to 5 amperes only on a 240 volts current supply. Therefore, it is certain to say that bigger wire is required on a 120 volts than on a 240 volts current supply. Example: 1.) For a 120 volt current supply: Current drawn = 1200 watts P = 10 amperes 120 volt supply E I 2.) For a 240 volt current supply we have: Current drawn 1200 watts 240 volts supply = 5 amperes From the foregoing example, it appears, that a smaller diameter wire on a 240 volts current can safely carry more cur- rent in proportion with its weight than a larger diameter wire on a 120 volts supply current. In effect, less copper is required to carry the same amount of power on a higher voltage current supply. If the basic wire insulation is rated at 300 volts, the same amount of power can be carried with less than one half the cost of copper. This is the main reason for the almost worldwide use of 240 volts current replacing the 120 volts line for practical and economical reasons. INTRODUCTION TO ELECTRICITY 1-1 Electricity Electricity is a form of energy generated by friction, induction or chemical change, having magnetic, chemical and radiant effect. In short, electricity is Electrons in motion. Electricity is one of the most useful discovery of man which paved the way to the numerous inventions from the simple tools to the most sophisticated gadgets making what originally seemed to be impossible become a reality. Contrary to some belief, electricity is not new. It has been here with us ever since and, its existence is as old as the universe which was discovered accidentally, by the ancient Greeks sometime in 600 B.C. However, the title of "Father of Electricity" was accredited to William Gilbert, an English Physicist after publishing his studies on the "Electric Attraction" and "The Electric Force." Electricity is a property of the basic particles of matter which like an atom, consists of: a) Electron b) Proton c) Neutron The Electron is the negatively charged particle of an Atom sometimes referred to as the negative charge of electricity. On the other hand, the Proton is the positively Power Voltage x Current P = V*I By Further Algebraic Manipulation of the Formula P = I2 * R I = P/V V = P/I R = P/I2 INTRODUCTION TO ELECTRICITY SOLUTION I = V/R; I = 240/50; I = 4.8 Amperes Where power factor (pf) in a purely resistive circuit, such as those with only electric heating elements, impedance or resistance power factor (pf) is equal to 1.0. Thus: W = VI * pf W = 240 * 4.8 * 1 W = I ^ 2 * R W = 1,152 watts W = (4.8)2 * 50 W = 1,152 watts ILLUSTRATION 1-6 A water heater draws 10 amperes at 240 volts current sup- ply. Determine its heat resistance. SOLUTION R = V/I R = 240/10 R = 24 Ohms Energy Calculations Determine the monthly energy consumption of the following appliances: ELECTRICAL LAYOUT AND ESTIMATE Appliances Load Daily Used Electric Iron Water Heater Toaster 1,200 watts 1,000 watts 2,300 watts 2 hours 3 hours 30 minutes SOLUTION Electric iron 1,200 w = 1.2 kw. x 2 hrs. = 2.4 kwh. Water Heater 1,000 w = 1.0 kw. x 3 hrs. = 3.0 kwh Toaster 1,300 w = 1.3 kw. x 0.5 hrs. = .65 kwh Total………..6.05 kwh. If the average cost of energy (not power) is P5.00 per kwh, for 30 days consumption, multiply: 30 x 6.05 181.50 kwh. per month x 5.00 Total cost.....P 907.50 1-9 Voltage and Voltage Drop Comparatively, in a Series Circuit - Current is the same throughout but voltage differs. In a Parallel Circuit, the Voltage is the same, but the cur- rent differs. Take note that in a parallel arrangement, all current loads cumulatively add. For instance, appliances and light loads connected to a parallel circuit has the same voltage imposed, but each load draws a different current according to its wattage rating. Another one important principle that is worthy to note is, "The sum of the voltage drop around a circuit is equal to the supply voltage." This principle is important in a series circuit. On a parallel circuit, each item has the same voltage across it, which 3. Cross Sectional Area of Wire. The bigger the cross sectional area of wire, the lower its resistance. 4. Temperature. Metal offers high resistance to high temperature (heat). ELECTRICAL LAYOUT AND ESTIMATE SOLUTION 1. Assume motor efficiency say 85% 2. 1-horse power is 746 watts, convert HP to watts. 746 x 2 1,492 watts 3. Efficiency= Output Input Input = 1.492 0.85 = 1,755 watts 4. For AC current Power = Volts x Amperes x power factor power factor = Power Volts x Amperes pf = 1,755 240 v. x 15 amp. pf = 0.4875 Volt-Amperes = 240 v. x 25 Volt-Amperes = 3,600 v.a. Take note the difference between volt-amperes and watts. 1-5 The Ohms Law In 1926, George Simon Ohm, a German scientist, discov- ered the relationship between the Current, Voltage and Resis tance now referred to as the Ohms Law which states that: ELECTRICAL LAYOUT AND ESTIMATE All other factors considered, the higher the circuit voltage, the more economical the system will be. The advantages of us ing high voltage for transmission and distribution line facilitate the conversion from one voltage to another that could not be done with the direct current (DC) but much easier with the al ternating current (AC). Example: The owner of a 5 kw. electric motor irrigation pump, re- quested line connection from the electric cooperative. The owner was given an option to avail of either 120 or 240 volts service. What is the good choice if the circuit line has a resis- tance of 42 Ohms? Solution in a Comparative Analysis 5kwis = 5 000 watts 120 volts 240 volts Current drawn (5000w)/(120v) = 41.66 ampere (5000w)/(240v) = 20.83 ampere Minimum wire size required to carry the current without overheating No. 8 AWG No. 12 AWG (see Table 1-1) Relative cost of the No. 8 and No. 12 wire in comparative ratio 2.2 1.0 Voltage drop 41.66 * 0.42 = 17.5v = 14.6% 20.83 * 42 = 8.75V . = 3.6% Advantages of the 240 volts over the 120 volt current supply 1. Smaller wire is required which means, lower in cost. ELECTRICAL LAYOUT AND ESTIMATE It is interesting to note that the capacity of the circuitry increases as the wire number decreases. The ratings of the wires apply only to copper wire be it solid or stranded types. Aluminum wires is not recommended for circuitry or house wiring. TABLE 1-2 LOAD LIMIT IN WATTS Circuit Capacity in Amperes Load Limit in watts 15 A 20 A 30 A 60 A 1800 W 2400 W 3600 W 7200 W CURRENT AMPERES – I = 15 – A POWER (WATTS) - P = 1800 W VOLTAGE VOLTS - E = 220 V connections wherein the lights constitute one parallel grouping and the convenience wall outlets constitute the second parallel grouping. ELECTRICAL LAYOUT AND ESTIMATE of electricity that weighs about 1850 times as much as the Electron. The Neutron is that particle of an Atom which is not electrically charged and weighs slightly more than the proton. Theory: 1. That, all matters are made up of molecules. 2. That, molecules are made up of atoms. 3. That, atom contains neutrons, electrons and protons. 4. That, neutron is neutral. It is neither positive or negatively charged. 5. That, the electron of an atom of any substance could be transformed into another atom. 1-2 Definition of Terms Ion is the term applied to an atom or molecule which is not electrically balanced. It is an atom or molecule that is electrically charged. It simply mean there is a loss or gain of one or more electrons. Ions occur when the electrons in the atom is loosened through friction by another atom. Therefore, the presence of electrons in any organic or inorganic substance is a fact, that electricity is always present. Volt or Voltage is the electrical pressure that causes the electrons to move through a conductor (wire). In other words, voltage is the electromotive force. Comparatively, to have 12 volts is like having 12 pounds of water pressure inside the pipe of a water system. Thus, the higher the voltage, the more electricity will be forced to flow. Volt was named after Alessandro Volta, an Italian scientist who discovered that electrons flow when two different metals are connected by a wire and then dipped into a liquid that con- duct or carry electrons. INTRODUCTION TO ELECTRICITY "The higher the voltage, the larger the current, and the higher the resistance, the lower the current." The relationship between the current, voltage and resistance is presented in the following equations known as the Ohms Law. I = V/R Where: I = Current flow (amperes) V = Electromotive force (volts) R= Resistance (Ohms) To Find the: * Voltage electrical pressure (volts) V = IR * Current (Ampere)............. I = V/R * Resistance (ohms)............ R = V/I ILLUSTRATION 1-3 Determine the current flow in a circuit having a resistance of 5 Ohms on a 120 volts and 240 volts current supply. (Circuit refers to the electrical wiring installation) SOLUTION 1. For 120 volts: I = V/R = 120/5 I = 24 amperes INTRODUCTION TO ELECTRICITY "The AC electricity is dangerous, because it involves high voltage transmission line." The AC advocates on the other hand, countered that: "The AC alternation is just like a handsaw which cuts on the upstroke and the down stroke. The high voltage in the transmission line could be reduced to the desired voltage as it passes the distribution line." Alternating Current or Voltage is a current or voltage that changes in strength according to a sine curve. An alternating current AC reverses its polarity on each alternation and reverses its direction of flow for each alternation. The AC current goes through one positive loop and one negative loop to form one complete cycle that is continuously repeated. The number of times this cycle of plus and minus loop occur per second is called the Frequency of alternating current AC expressed in cycles per second normally referred to as Hertz (hz) named after H.R. Hertz. The frequency of the Direct Current DC is obviously zero Hertz. The voltage is constant and never changes in polarity. A circuit operating at increased voltage, has a lower power loss, power voltage drop, and economically constructed for using smaller copper wires. On transmission and distribution line, power loss is the most important problem to resolved. This is the main reason why Alternating Current AC gained more favor and acceptance during the middle part of the 19th century. In the USA, an ordinary house current is described as 120 volts 60 hertz. Resistance ILLUSTRATION 1-5 A mercury lamp having a hot resistance of 50 Ohms, is connected to a socket with 240 v. current supply. a. How much current, flows through the lamp? b. Calculate the power drawn 16 Electrical fundamentals & safety standards (Electrical theories & formulas) by Adrian T. Blasco A Baby Thesis Submitted to Mr. Eduardo L. Teves Valencia Technical Vocational High School In Fulfillment of the Requirements For the 4TH Quarter Grade April 2024