Electricity | Grade 8 Science DepEd MELC Quarter 1 Module 5 Part 1 Voltage, Current, Resistance

[Music] in this video we are going to discuss about electricity electricity has become a vital part of our lives the discovery of electricity has changed the way we work play and go about our daily routines the moment we wake up we use our smartphones to check for notifications in social media in the evening we use light bulbs to see clearly in fact we are surrounded with devices and machines that use electricity electricity has become so important that if taken away life comes to a standstill have you ever noticed birds sitting on electrical wires on the streets how can these birds sit on high voltage power lines without getting electrocuted it is not uncommon for a character in the movies to end up with a blackened face and head full of frizzy hair if they come in contact with electricity this makes for a good gag on screen however this will end up killing us in real life unless if we are birds birds have no problem sitting unruffled on the high voltage power lines [Music] electricity is the movement of electrons the movement of electrons through a device like our tv is what gives it the energy to display images and produce sound the electrons are essentially being pulled from the ground by the power station they move through the power lines through our tv and eventually they make their way back into the ground from where they came this creates a closed loop which is required for electricity to flow the other thing electrons need in order to move is motivation or more specifically a difference in what's called electrical potential when a bird is perched on a single wire its two feet are at the same electrical potential so the electrons in the wires have no motivation to travel through the bird's body no moving electrons means no electric current the bird is safe for the moment anyway if that bird stretches out a wing or a leg and touches a second wire especially one with a different electrical potential it will open a path for the electrons right through the bird's body there are other perils for our feathered friends the wooden pole supporting the wires is buried deep in the ground so it will also be dangerous for a bird to sit on the wire and touch the pole [Music] this is the problem that we encounter if we touch live wires since we are almost always in contact with the ground our bodies turn out to be excellent conductors of electricity and the electrical current will happily use them to complete a closed path to flow from high potential which is the wire to low potential which is the ground electricity is the movement of electrons electrons create charge which we can harness to do work our phone our light bulbs our television and many other gadgets and machines all harness the movement of the electrons in order to do work they all operate using the same basic power source electricity the three basic principles for this module can be explained using electrons or more specifically the charge they create voltage current and resistance voltage is the difference in charge between two points current is the rate at which charge is flowing resistance is the tendency of materials to resist the flow of charge so when we talk about these values we are really describing the movement of charge and the behavior of electrons a circuit is a closed loop that allows charge to move from one place to another components in the circuit allow us to control this charge and use it to do work through machines or any output anyway we will be talking more about circuits in a separate video [Music] george ohm was a bavarian scientist who studied electricity ohm starts by describing a unit of resistance that is defined by current and voltage so let's start with voltage and go from there we define voltage as the amount of potential energy between two points on a circuit one point has more charge than another this difference in charge between the two points is called voltage it is measured in volts which technically is the potential energy difference between two points that will impart one joule of energy per column of charge that passes through it the unit volt is named after the italian physicist alessandro volta who invented the first chemical battery voltage is represented in equations and schematics by the letter v when describing voltage current and resistance a common analogy is a water tank in this analogy charge is represented by the amount of water voltage is represented by the pressure of water and current is represented by the flow of water consider a water tank at a certain height above the ground at the bottom of this tank there is a hose the pressure at the end of the hose represents voltage the water in the tank represents charge the more water in the tank the higher the charge the more pressure is measured at the end of the hose likewise the less water in the tank the lower the charge the less pressure is measured at the end of the hose we can think of this tank as a battery a place where we store a certain amount of energy and then release it if we release a certain amount of water from the tank the pressure created at the end of the hose goes down we can think of this as decreasing voltage like when a flashlight gets dimmer as the batteries run down there is also a decrease in the amount of water that will flow through the hose less pressure means less water is flowing which brings us to current voltage can be generated by means other than rubbing certain types of materials against each other chemical reactions like batteries radiant energy like solar cells and the influence of magnetism on conductors like generators are a few ways in which voltage may be produced for now we won't go into detail as to how each of these voltage sources works it is more important that we understand how voltage sources can be applied to create charge flow in an electric circuit let's take this as a symbol for a chemical battery all right since we're done with voltage let's talk about current as long as the battery continues to produce voltage and the continuity of the electrical path isn't broken charge carriers will continue to flow in the circuit we can think of the amount of water flowing through the hose from the tank as current the higher the pressure the higher the flow and vice versa following the metaphor of water moving through a pipe this continuous uniform flow of charge through the circuit is called the current so long as the voltage source keeps pushing in the same direction the charge carriers will continue to move in the same direction in the circuit this single direction flow of current is called a direct current or dc with water we would measure the volume of the water flowing through the hose over a certain period of time with electricity we measure the amount of charge flowing through the circuit over a period of time current is measured in amperes usually just referred to as amps an ampere is defined as 6.241 times 10 to the 18th power electrons or one column per second passing through a point in a circuit amps are represented in equations by the letter i the unit ampere represented by a capital letter a is named after andre marie ampere a french physicist who made important contributions to the theory of electricity and magnetism let's say for instance that we have two tanks each with a hose coming from the bottom each tank has the exact same amount of water but the hose on one tank is narrower than the hose on the other tank we measure the same amount of pressure at the end of either hose but when the water begins to flow the flow rate in the tank with the narrower hose becomes lesser than the one with the wider hose in electrical terms the current through the narrower hose is less than the current through the wider hose if we want the flow to be the same through both hoses we have to increase the amount of water which is the charge in the tank with a narrower hose this increases the pressure or the voltage at the end of the narrower hose pushing more water through the tank this is analogous to an increase in voltage that causes an increase in current now we're starting to see the relationship between voltage and current but there is a third factor to be considered here the width of the hose in this analogy the width of the hose is the resistance this means we need to add another term to our model water equals charge measured in columns pressure equals voltage measured in volts flow equals current measured in amperes or amps for short and hose width equals resistance now let's proceed to resistance [Music] consider again our two water tanks one with a narrow hose and one with a wide hose it stands to reason that we can't fit as much volume through a narrow hose than a wider one the same pressure this is resistance the narrow hose resists the flow of water through it even though the water is at the same pressure as the tank with the wider hose [Music] in electrical terms this is represented by two circuits with equal voltages and different resistances the circuit with a higher resistance will allow less charge to flow meaning the circuit with higher resistance has less current flowing through it this brings us back to georgeon om defines the unit of resistance of one ohm as the resistance between two points in a conductor where the application of 1 volt will push 1 ampere recall that an ampere is equal to 6.241 times 10 raised to the 18th power electrons this value is usually represented in schematics with the greek letter omega and pronounced om different materials have different amounts of resistance conductors have very little resistance and therefore allow more charges to pass through insulators are materials that have very high resistance and therefore the flow of charges would be difficult the length and thickness of the conducting wire are factors that affect resistance encountered by current the longer the wire the greater will be its resistance the greater the cross sectional area which is a measure of the thickness of the wire the lower will be its resistance the resistance of an object also changes when the object becomes wet dry human skin for instance has a resistance of 100 000 ohms but when it gets wet its resistance is reduced to 1000 ohms that is why it is important to use dry hands when plugging an electrical appliance to reduce any chances of getting a lot of current if an accident occurs electric charges can be made to move through a conducting material the electric charges are the electrons of the conducting material materials such as copper steel and aluminum have a lot of loosely held electrons which makes them good conductors of electricity current is a measure of the number of charges passing through a cross section of a conductor on a given time what is the direction of current a battery has terminal marks positive or plus and negative or minus the plus sign indicates surplus or excessive charge and the minus sign means deficiency the movement of charges from the positive side of the battery to the negative side is called conventional current or simply current however this is not the actual motion of electrons in a circuit the direction of the flow of electrons is from the negative terminal to the positive terminal this is called electron current the direction of current does not affect what the current does because electric current is composed of individual charge carriers flowing in unison through a conductor by moving along and pushing on the charge carrier's head the amount of flow throughout a single circuit will be the same at any point if we were to monitor a cross section of the wire in a single circuit counting the charge carriers flowing by we would notice the exact same quantity per unit of time as in any other part of the circuit regardless of conductor length or conductor diameter if we break the circuit's continuity at any point the electric current will cease in the entire loop and the full voltage produced by the battery will be manifested across the brake between the wire ends that used to be connected an ammeter measures electric current because the device measures how much charge flows in a certain cross-section at the given time it has to be connected in series take note how the positive and negative signs of the ammeter and the terminals of the battery are oriented [Music] energy is needed to make the charges move in the previous module we learned that when work is done on an object energy is transferred the voltage of a battery does the work on charges to make them move batteries are energy sources the chemical energy in the battery is transformed to electrical energy this electrical energy moves the charges in a circuit the work done on the charges as it passes through a load is measured as the voltage across the load a voltmeter measures voltage the voltmeter must be connected parallel or across the load the positive terminal of a voltmeter is connected to the positive terminal of the bulb while the negative terminal is connected to the negative terminal of the bulb now how are these three related let's start first with the relationship between voltage and current voltage and current are two fundamental quantities in electricity voltage is the cause and current is the effect the higher the voltage the higher the current thus they are directly proportional on the other hand the relationship of resistance and current is inversely proportional the lower the resistance the higher the current now let's wrap things up electricity is the movement of electrons electric charges are the electrons of the conducting materials voltage is the difference in charge between two points current is the rate at which charge is flowing and resistance is the tendency of materials to resist the flow of charge or current that's all for now stay tuned for our next video where we will be discussing how current voltage and resistance affect each other through the ohm's law see you on our next video and don't forget to keep your minds busy if you like this video please subscribe to our channel and hit the notification icon for more videos like this

Channel: The Learning Bees

Views: 62,903

Keywords: The Learning Bees, Department of Education, DepEd, MELC-Based, Most Essential Learning Competencies, Science, Grade 8, Electricity, Voltage, Current, Resistance, Coulomb, Ampere, Volt, Ohm, Ohm's Law, Electric charges, Why birds don't get electrocuted on wires, Electrons, Circuit, Georg Ohm, Electricity water analogy, Generator, Solar cells, Battery, Andre-Marie Ampere, Conductor and insulator, Ammeter, Voltmeter, Energy

Id: S7WMIF5Qfhw

Length: 19min 41sec (1181 seconds)

Published: Sat Nov 14 2020