Basic Electrical Quantities (SY 2024-25) PDF

quantities BASIC ELECTRICAL Engr. Christian S. Nabio Instructor I TOPICS 1. Nature of Electricity 2. Electrical Quantities (Charge, Power and Energy) I. Introduction: The Nature of Electricity Atomic structure of four common elements THE ELECTRIC CHARGE THE COULOMB...

quantities BASIC ELECTRICAL Engr. Christian S. Nabio Instructor I TOPICS 1. Nature of Electricity 2. Electrical Quantities (Charge, Power and Energy) I. Introduction: The Nature of Electricity Atomic structure of four common elements THE ELECTRIC CHARGE THE COULOMB The magnitude of electric a body possesses by the of electrons compared the number of protons within. The symbol for the magnitude of the electric charge (Q), is expressed in units of coulombs (C). A charge of one -Q, means a body a charge of 6.24 x 1018 more electrons The fundamental of an electric is its ability to exert a force. This force is present within the electrostatic field surrounding object. Draw the electrostatic field that would exist between two negatively charged objects. When two like charges are placed near each other, the lines of force repel each other as shown. POTENTIAL DIFFERENCE (VOLTAGE (v)) Because of the force of its field, an electric field has the ability to do work of moving another charge attraction or repulsion The ability of a charge to do work is called its potential. When one charge is different from the other, there must be a difference in potential between them.  The sum of the differences of potential of all the charges in the field is referred to as electromotive force (emf). The basic unit of potential difference is volt (V). The symbol for potential difference is V, indicating the ability to do work of forcing electrons to move. Potential difference is called voltage. - an external electromotive force (emf) - also called potential difference - the energy required to move a unit charge through an element - measured in volts (V)  SOURCES OF ELECTRICITY 1.Chemical Battery / Dry Cell 2.Generator 3.Solar Cells 4.Piezoelectric 5.Photoelectric effects 6.Thermocouple 1. Battery A chemical cell is a combination of materials which are used for converting chemical energy into energy. Dry cell batteries create electrical energy by converting chemical energy into electricity. The exact means of doing so depends on the type of dry cell battery in question, but the materials that are used are generally zinc and carbon or zinc and manganese dioxide. These materials are placed within the electrolyte paste within the battery. They react with each other through a chemical process in which the electrolyte (carbon or manganese dioxide) reacts with the zinc, creating electricity. This is transmitted out of the battery using positive and negative electrodes. 2. Generator 3. Solar Cells Solar cells convert light energy directly into electric energy. They consist of semiconductor material like are used in large arrays in spacecraft to recharge batteries. Solar cells are also used in home heating. 4. Piezoelectric Effect Certain crystals, such as quartz and Rochelle salts, generate a voltage when they are vibrated mechanically. This action is known as the piezoelectric effect. 5. Photoelectric Effect Some materials, such as zinc, potassium, and cesium oxide, emit electrons when light strikes their surfaces. This action is known as the photoelectric effect. 6. Thermocouples If wires of two different metals, such as iron and copper, are welded together and the joint is heated, the difference in electron activity in the two metals produces an emf across the joint. Thermocouple junctions can be used to measure the amount of current because current acts to heat the junction. II. Electrical Quantities CHARGE (q) - an electrical property of the atomic particles of which matter consists - measured in coulombs (C) Benjamin Franklin (1706-1790) American scientist and inventor When a conducting wire (consisting of several atoms) is connected to a battery (a source of electromotive force), the charges are compelled to move; + charges move in one direction while – charges move in the opposite direction. POINTS TO NOTE ABOUT ELECTRIC CHARGE: ✓ Coulomb is a large unit for charges In 1 C of charge, there are 1/(1.602 x 10-19) = 6.24 x 1018 electrons Thus, realistic or laboratory values of charges are on the order of pC, nC, or μC. POINTS TO NOTE ABOUT ELECTRIC CHARGE: ✓ According to experimental observations, the only charge that occur in nature are integral multiples of the electronic charge e = -1.602 x 10-19 C ✓ The law of conservation of charge states that: “charge can neither be created nor destroyed, only transferred.” Thus, the algebraic sum of the electric charge in a system does not change Alessandro Antonio Volta (1775-1836) ✓ Italian physicist ✓ Invented the electric battery in 1796, which provided the 1st continuous flow of electricity, and the capacitor VOLTAGE (v) ❖ Signal – term used for an electric quantity, such as current or a voltage, when it is used for conveying information. ❖ DC Voltage – commonly produced by a battery ❖ AC Voltage – commonly produced by an electric generator Andre-Marie Ampere (1775-1836) ✓ French mathematician and physicist ✓ Laid the foundation of electrodynamics ✓ Defined the electric current and developed a way to measure it in 1820s CURRENT (i) The movement or the flow of electrons is called current. To produce current, the electrons must moved by a potential difference. Current is represented by the letter symbol I. The basic unit in which current is measured is the ampere (A). One ampere of current is defined as the movement of one coulomb past any point of a conductor during one second of time Current flow a) Conventional flow of current – the electron charge flow from positive terminal to negative terminal b) Non-conventional flow of current – the electron charge flow from negative terminal to positive terminal RELATIONSHIP BETWEEN CURRENT, CHARGE, AND TIME  Current doesn’t need to be a constant-valued function RELATIONSHIP BETWEEN CURRENT, CHARGE, AND TIME  CURRENT - a current that remains - a current that varies constant with time sinusoidally with time DIRECT CURRENTS AND VOLTAGES Direct current (dc) is current that moves through a conductor or circuit in one direction only. What is an ELECTRIC CIRCUIT? - an interconnection of electrical elements A simple electric circuit A complicated real circuit POWER (p) - the time rate of expending or absorbing energy - measured in watts (W) POWER (p) a time-varying quantity and is called instantaneous power ENERGY - capacity to do work - measured in joules (J) CIRCUIT ELEMENTS - an element is the basic building block of a circuit - an electric circuit is simply an interconnection of the elements – process of determining voltages across the elements of the circuit  Elements found in Electric Circuits - not capable of generating - capable of generating energy energy (e.g., resistors, (e.g., generators, batteries, and capacitors, and inductors) operational amplifiers)  THANK YOU! Proverbs 3:5-6 “Trust in the LORD with all you heart, and lean not on your own understanding; in all your ways acknowledge Him and He will make your paths straight.”