Electrical Circuits 1 Reviewer PDF

ELECTRICAL CIRCUITS 1 If this 29th electron gains sufficient energy from the surrounding medium to leave the parent atom, it is called a REVIEWER free ele...

ELECTRICAL CIRCUITS 1 If this 29th electron gains sufficient energy from the surrounding medium to leave the parent atom, it is called a REVIEWER free electron. In 1 cubic inch of copper at room temperature, there are approximately 1.4 x1024 free electrons. INTRODUCTION ELECTRIC CHARGE An electron is the smallest particle with a negative ELECTRICITY charge, equal in magnitude to a proton’s positive charge. Form of energy resulting from the existence of Electrical charge (Q) arises from an imbalance of charged particles (such as electrons or protons), either electrons: excess electrons create a negative charge, while statically as an accumulation of charge or dynamically as a deficiency results in a positive charge. Static electricity is a current. the presence of a net charge in a material. ATOMIC STRUCTURE STATIC ELECTRICITY An atom is the smallest unit of an element, Rubbing a balloon on a pullover transfers retaining its properties. All matter consists of atoms made electrons to the balloon, making it negatively charged, up of electrons, protons, and neutrons. Understanding while the pullover becomes positively charged. The current and voltage starts with knowing an atom's opposite charges attract, causing them to stick. structure. LIGHTNING The orbiting electron carries a negative charge Heavier, negatively charged particles sink to the equal in magnitude to the positive charge of the proton. In general, the atomic structure of any stable atom has an bottom of the cloud. When the positive and negative equal number of electrons and protons. charges grow large enough, a giant spark - lightning - occurs between the two charges within the cloud. This is like a static electricity sparks you see, but much bigger AC AND DC SOURCES AC (Alternating Current) changes direction periodically and operates at a specific frequency (e.g., 50 Hz or 60 Hz). It is generated by alternators, suitable for long-distance transmission due to low energy loss, and Copper is the most commonly used metal in the commonly used for household power and industrial electrical/electronics industry. systems. DC (Direct Current) flows in one constant direction with a steady voltage. It is produced by batteries or solar panels, ideal for low-voltage applications like electronics, but inefficient for long-distance transmission. GENERATION OF AC VOLTAGE An ac voltage is one that continually changes in magnitude and periodically reverses in polarity. An AC voltage can be produced by a generator called alternator. It came form the theory of electromagnetic induction, “Whenever the flux linking a coil changes an emf is included.”. DC GENERATOR  MAGNETISM DEFINITION: In physics, magnetism is one of the phenomena by which materials exert attractive or repulsive forces on other materials. Magnets produce magnetic forces and have magnetic field lines and have two ends or poles, called north and south poles. At the poles of a magnet, the magnetic field lines are closer together. ELECTRICITY AND MAGNETISM On 21 April 1820, during a lecture, Hans Christian Oersted, a Danish physicist and chemist, and a professor noticed a compass needle deflected from magnetic north when an electric current from a battery was switched on and off, confirming a direct relationship between electricity and magnetism. ELECTROMAGNETISM a magnetic field that is produced by a current of electricity  GALVANOMETER is an electromagnet that interacts with a permanent magnet. The stronger the electric current passing through the electromagnet, the more is interacts with the permanent magnet. ELECTROMAGNETIC INDUCTION Electromagnetic induction is the process where a conductor in a changing magnetic field (or moving through a stationary field) produces a voltage, which induces an electrical current. Discovered by Michael Faraday in 1831 and independently by Joseph Henry in 1832. ▪ Current is only produced if the magnet is moving because a changing magnetic field is what creates current. ▪ If the magnetic field does not change, such as when the magnet is stationary, the current is zero.  BASIC ELECTRICAL QUANTITIES AMPERE One ampere (1 A) is the amount of current that exists when a number of electrons having a total charge of one coulomb (1 C) move through a given cross-sectional VOLTAGE area in one second (1 s). Voltage, symbolized by V, is defined as energy or work per unit charge. 𝑉 = 𝑊/𝑄 Where: V is voltage in volts (V), W is energy in joules (J), Q is charge in coulombs (C) Some sources use E instead of V to symbolize voltage. CURRENT SOURCE Voltage provides energy to electrons, allowing An ideal current source provides a constant them to move through a circuit. This movement of current for any load, similar to how an ideal voltage source electrons is the current, which results in work being done provides constant voltage. While an ideal current source in an electrical circuit. doesn't exist, it can be approximated in practice. One VOLT is the potential difference (voltage) between two points when one joule of energy is used to move one coulomb of charge from one point to the other. Resistance is the opposition to current flow, symbolized as R and measured in ohms (Ω). One ohm of resistance VOLTAGE SOURCE allows one ampere of current when one volt is applied A voltage source provides electrical energy or across the material. electromotive force (emf), more commonly known as voltage. Voltage is produced by means of chemical energy, RESISTOR light energy, and magnetic energy combined with A resistor is a component designed to provide a specific mechanical motion. resistance. It is used to limit current, divide voltage, or generate heat. Resistors are categorized as either fixed or variable. FIXED RESISTORS Fixed resistors have predetermined resistance values set during manufacturing and cannot be easily adjusted. CURRENT Electrical current is the rate of flow of charge. Current in a conductive material is determined by the number of electrons (amount of charge) that flow pass a point in a unit of time. 𝑰=𝑸/ t Where: I is current in amperes (A) (A), Q is charge in coulombs (C), t is time in seconds (s). Electrical current is the rate of flow of charge.  RESISTANCE AND RESISTIVITY TEMPERATURE EFFECT Inferred Absolute Temperature For good conductors, increase in temperature results in an Resistance of any material is due primarily to the following factors: increase in the resistance level. For Copper(and most 1. Material other metallic conductors), the resistance increases 2. Length almost linearly. 3. Cross-sectional area 4. Temperature The first three elements are related by the following basic equation for resistance: WHERE: 𝜌 =resistivity, 10.37 CM-Ω/ft at 20⁰C for copper 𝑙 =length, ft A = area in Circular Mils, CM CIRCULAR MILS (CM) Temperature Coefficient of Resistance The temperature coefficient of resistance is the rise in the resistance of a material per degree rise in temperature to the original resistance. Where: T1 = lower value temperature T2 = Higher value temperature R1 = resistance at T1 R2 = resistance at R2 𝛼1 = temperature coeff. of resistance at T1 EXAMPLES  Temperature Coefficient of POWER AND ENERGY Resistance POWER - rate of doing work - rate at which energy is used WHERE: P = power, watts W = energy, joules t = time, seconds WHERE: P = power, watts V = voltage, volts I = current, amperes Variation of Resistance with given temperature OHM’S LAW Ohm’s law states that current is directly proportional to voltage and inversely proportional to resistance. In formula, VOLTAGE DIVIDER RULE States that the voltage across a resistor in a series circuit is equal to the value of that resistor times the total applied voltage divided by the total resistance of the series configuration. KIRCHHOFF’S CURRENT LAW The law states that the algebraic sum of the CURRENT DIVIDER RULE currents entering and leaving a junction (or region) of States that the current through any branch of a a network is zero. parallel resistive network is equal to the total resistance of the parallel network divided by the resistor of interest and multiplied by the total current entering the parallel where Σ represents summation I the currents entering and leaving the junction The law can also be stated in the following way: The sum of the currents entering a junction (or region) of a network must equal the sum of the currents leaving the same junction (or region). In equation form, KIRCHHOFF’S LAWS specifies that the algebraic sum of the potential rises and drops around a closed path (or closed loop) is zero. In symbolic form it can be written as Where: Σ represents summation; ⟳the closed loop V the potential drops and rises.  METHODS OF ANALYSIS NODAL ANALYSIS CURRENT SOURCES The current source is often described as the dual of the voltage source. The term dual is applied to any two elements in which the traits of one variable can be interchanged with the traits of another. A current source determines the direction and magnitude of the current in the branch where it is located. The magnitude and the polarity of the voltage across a current source are each a function of the network to which the voltage is applied. BRANCH CURRENT METHOD LOOP CURRENT METHOD