ฝึกพูดภาษาอังกฤษด้วยเทคนิค Shadowing จากวิดีโอ: 120V 240V Electricity explained - Split phase 3 wire electrician
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169 ประโยค
หากประโยคสั้นหรือยาวเกินไป กดที่ Edit เพื่อปรับแก้
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Hey there guys Paul here from TheEngineeringMindset .com.
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In this video we're going to be learning how three wire split phase electricity supplies work to get 120 and 240 volts.
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We'll look at how the electricity gets from the power station over to the property
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and then how it's connected around the property and each of the main components.
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Now this system is used in North America us will be using their terminology
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and color coding if you're from outside this region then you can still follow along
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but your electrical system will work differently we've covered
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that in a separate video do check
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that out links are in the video description down below remember electricity is dangerous
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and can be fatal you should be qualified
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and competent to carry out any electrical work so electricity is generated at the power station which is usually located far away.
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The power station generates AC alternating current and is connected to a step up transformer.
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This transformer increases the voltage to reduce losses and is connected to the grid.
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The grid carries high voltage electricity over long distances over to the towns and cities.
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Once it reaches the towns and cities it will enter a step down transformer
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which will decrease the voltage to a safer level.
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From here it will be distributed locally into smaller circuits on on different streets or groups of properties.
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Connected to these distribution cables will be smaller transformers,
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usually pole -mounted, which again reduce the voltage down even further to a level safe enough for residential use.
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On the property will be an electricity meter
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which will quantify how much electricity has been used and the electricity company will use this to invoice the property.
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The transformer will be connected to the electricity meter by some cables which will either run above ground or underground.
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these cables will be two hot wires
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and a neutral wire inside the transformer
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we have two coils of wire the primary coil is connected to the power station
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and the second coil will be connected to the property the
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two hot wires are connected to each end of the secondary coil
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and the neutral is connected to the center of the coil now don't worry about
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that too much for now we're going to look at this again later in the video to understand it
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so if we zoom into the property we find a main service panel
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which is sometimes called a load center or breaker box.
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If we remove the cover and look inside we first find the main breaker.
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This is usually at the top of the panel but it might be at the bottom.
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The two hot wires from the electricity meter will connect directly to the lugs on the main breaker.
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Coming out of the main breaker will be two main bus bars.
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These are basically exposed metal sheets
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which carry electricity to the circuit breakers notice i've shown the current flowing backwards
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and forwards that's because this is ac
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or alternating current these bus bars as well as the lugs are not insulated they are live or hot
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the main breaker can be manually flipped to cut the power
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to everything downstream of the main breaker the main breaker will also provide over current protection to the property
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it is rated to handle a certain amount of electrical current passing through it typically between 100 and 200
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If this value is exceeded then it will trip automatically to try and protect the property and its electrical circuits.
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Inside the panel we also have a neutral and ground bus bar.
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This is basically a strip of metal with lots of holes and screws in it.
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The neutral and ground wires will sit in the holes and the screws will lock them in place.
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In this example we have a block on either side of the panel.
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As this is a main panel the two bus bars can be joined together
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so so we have a connector bar between them.
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That way we have a shared neutral ground bus bar.
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Sub panels must have their bar separated, but that's a topic for a separate video.
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From the electricity meter, we will have the neutral wire connected to the lug on the top of the neutral ground bar.
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Notice the green screw.
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This is bonding the neutral bar to the metal casing of the service panel.
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The purpose of the neutral bar is to return the used electricity back to the transformer.
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It does actually get a little bit more advanced than that, but we're going to look at that in a more advanced complex video.
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This is just covering the basics.
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So the two hot wires will provide electricity
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and once it is used it will return to the transformer via the neutral bar.
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It is still AC alternating current
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but to make it easier to visualize I've only animated the current flowing in one direction
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so you can see the path it will take.
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Now if we were to take our multimeter
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and connect one lead to the bus bar
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and the other lead to the neutral bar we would get a reading of around 120 volts.
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If you don't already have a multimeter, then I highly encourage you to get one for your toolkit.
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It's essential for any electrical testing and fault finding.
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Links down below for which one to get and from where.
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If we connect the multimeter leads to the other bus bar and the neutral bar, we would again get a reading of around 120 volts.
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But if we connect the multimeter leads to the two bus bars, then we get a reading of double that at around 240 volts.
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So why is that?
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What's happening here?
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So when we look at how the transformer is connected to the main panel,
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we have the two hot bus bars connected to either end of the secondary coil in the transformer.
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And then we take the neutral bus bar connected to the center of the secondary coil.
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So basically, when we connect across the bus bar and the neutral bar, we're only using half of the coil
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so we are only picking up half the electrical voltage the transformer can provide so that way we get 120 volts.
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When we connect to the two bus bars we're connecting to the full length of the coil
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so we're picking up the full voltage which the transformer can provide therefore we get 240 volts.
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If you want to learn how transformers work then check out our video on transformer basics links for
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that down in the video description below.
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Now coming back to the panel connected
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Connected to the bus bar, we'll have our circuit breakers.
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These will look something like this with this black plastic casing and a toggle switch on top.
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The circuit breaker controls the flow of electricity into individual circuits in the property.
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It can be manually tripped to cut the power, but it also has two important features.
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The first feature is overload protection.
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The circuit breaker is rated to handle a set amount of electrical current.
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When appliances or lights are connected to the circuit, they will each increase the current in the circuit.
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If too many things are plugged in and turned on, then eventually the current will be more than the breaker can handle
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and the breaker will automatically trip to cut the power off to the circuit and protect the property.
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The second feature is short circuit protection.
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When the hot and neutral come into direct contact with each other, the current will dramatically increase almost instantly.
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When this occurs, it creates a magnetic field which will trip the breaker and cut the power automatically.
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Let's have a look at how the circuit breaker is connected to the electrical circuit.
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In this example we will connect to a simple light fitting which is controlled by a switch.
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We take the hot wire from the circuit breaker and run this to the switch.
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We then run another wire from the switch and over to the light fitting.
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From the light fitting we have a neutral wire which carries the return current back to the neutral bus bar.
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We take the ground wire from the metal casing of the ceiling box in the switch
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and we also join this to the neutral bus bar as in this case it's shared.
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The purpose of the hot wire is to carry the electrical current over to the light fitting.
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The purpose of the neutral wire is to carry the used electrical current back to the main panel
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and then back to the transformer.
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The purpose of the ground wire is to provide protection for a fault current.
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If for example the hot wire came loose
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and touched the metal casing of the light fitting the ground wire provides a low resistance path back to the panel.
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Without this path electricity could flow through you if if you touch the metal box.
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As the current flows through the ground wire, it will increase the current and that will trip the breaker automatically.
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So the electricity flows through the hot wire, through the main breaker, down the main bus bar and into the circuit breaker.
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From there, it flows along the hot wire, across the switch and light, then back along the neutral wire and into the neutral bus bar,
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along the neutral bus bar wire and back to the transformer.
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I've animated this using AC alternating current, but to make it easier to understand the path, I've shown it flowing in a single direction now.
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We've covered lighting circuits in detail in a separate video, do check that out, links in the video description below.
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Okay so what else might we find here?
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Well we might find a double pole circuit breaker
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which will let us connect to both bus bars to get 240 volts
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which we can use to power larger appliances like dryers, ranges and air conditioning units.
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If we look at the dryer circuit example we run the red hot wire from the circuit breaker
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which is connected to the main bus bar number two and we run this to the receptacle.
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Then we run our black hot wire from the other terminal of the circuit breaker
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which is connected to bus bar one and we connect that to the receptacle also.
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In this case we have the neutral wire connected between the neutral bus bar
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and the receptacle which will allow us to get either 120 or 240 volts from the outlet.
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Then we have a ground wire to provide a safe route for any fault current.
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Now we can either connect across the two hot wires for our 240 volt connection
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or between the hot wire and the neutral wire to get 120 volt connection.
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We'll also very likely find a GFCI circuit breaker which stands for ground fault circuit interrupter.
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This will look something like this
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and depending on the model you buy you will usually have a pigtail neutral wire connected to it.
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GFCIs are required on certain circuits where outlets are used for places like kitchens,
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bathrooms, hot tubs etc. You should check with the National Electric Code for exact details.
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The GFCI breaker has both the hot and the neutral flowing through it.
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This way you can measure the current flowing through both wires and ensure they are equal.
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If we took a standard outlet, we would take a hot wire from the breaker and connect this to the outlet terminal.
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Then we take the neutral wire and run this back directly to the circuit breaker to a specific neutral terminal.
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We then connect the pigtail wire into the neutral bus bar.
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This will provide the return path.
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And of course we run the ground wire from the outlet back to the neutral ground bar.
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If we look at this example, the current is flowing normally until the guy sticks a screwdriver into the socket.
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The electricity then flows through him instead of the neutral wire.
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The GFCI is measuring the current in the two wires and notices that these are not equal.
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It then automatically trips the breaker to cut the power and save the man's life.
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We might also come across an AFCI circuit breaker.
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This stands for arc fault circuit interrupter.
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These are required for circuits feeding bedrooms, hallways, kitchens, et cetera.
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Again, check with the National Electric Code for exact details.
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AFCIs work also by being connected to both the hot and neutral wires.
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Inside this circuit breaker is a circuit board, which is measuring the circuit and monitoring for patterns which indicate an arc fault is occurring.
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These are installed pretty much identically to how we saw the GFCI breaker.
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Under normal conditions the current flows through the hot, back through the neutral, into the breaker, then through the pigtail and back through the neutral bar.
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But if for example a screw was accidentally inserted very close to the cable
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and removed the insulation to expose the copper wires, the electricity could now potentially jump across or arc from the hot wire and into the neutral.
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The arc is incredibly hot and causes most residential electrical fires.
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As the arc occurs it creates a unique signal in the electrical cable.
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The circuit breaker can detect this and will automatically trip to cut the power.
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Connected to the neutral ground bar will be a thick uninsulated copper wire
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which runs out of the bottom of the panel
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and off to the ground rod which is pushed into the earth near the property.
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Under normal circumstances no electrical current will flow through this wire
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its purpose is to dissipate high static voltages from things like lightning this way the electrical systems
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and equipment is protected from damage additionally we'll also find a bonding wire to metal pipe work in the property
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this is to provide a safe route for electricity to flow
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should a hot wire come into contact with a metal pipe
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and this way it will prevent a person being electrocuted
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if they were to touch the pipe work okay guys that's it for this video
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but if you want to continue your learning then check out one of the videos on screen now
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and i'll catch you there for the next lesson.
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Don't forget to follow us on Facebook, Twitter, Instagram, as well as
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คำศัพท์และข้อสังเกตด้านการพูดสำหรับบทเรียนนี้
บทเรียนฝึกพูดนี้ใช้วิดีโอ “120V 240V Electricity explained - Split phase 3 wire electrician” เป็นสื่อ คำที่ถูกพูดซ้ำบ่อยที่สุด: wire, neutral, bar, breaker, circuit วิดีโอนี้มี 169 ประโยค และ 2404 คำ สำหรับฝึกพูดตาม ช่วงที่มีเสียงพูดยาว 12:10 ผู้พูดพูดเร็ว ประมาณ 198 คำต่อนาที จึงมีการเชื่อมเสียงและลดเสียงค่อนข้างมาก มีเพียง 79% ของคำที่อยู่ใน 3,000 คำที่ใช้บ่อยที่สุดในภาษาอังกฤษ คำศัพท์จึงค่อนข้างยาก
คำศัพท์สำคัญในวิดีโอนี้
คำที่ควรเรียนรู้ 15 คำจากวิดีโอ พร้อมคำอ่านและความหมาย:
| คำศัพท์ | คำอ่าน | ความหมาย |
|---|---|---|
| wire คำนาม | /ˈwaɪɚ/ | ลวด, สาย |
| neutral คำคุณศัพท์ | /ˈnuː.tɹəl/ | เป็นกลาง |
| connect คำกริยา | /kəˈnɛkt/ | เชื่อม, ต่อ |
| voltage คำนาม | /ˈvəʊltɪd͡ʒ/ | แรงดันไฟฟ้า, โวลเตจ |
| metre คำนาม | /ˈmiːtəɹ/ | เมตร |
| occur คำกริยา | /əˈkɜː/ | เกิด |
| terminal คำนาม | /ˈtɚmɪnəl/ | อาคารผู้โดยสาร |
| copper คำนาม | /ˈkɒpə/ | ทองแดง |
| pole คำนาม | /pəʊl/ | ขั้ว, ขั้วโลก |
| grid คำนาม | /ɡɹɪd/ | ตาราง |
| rat คำนาม | /ɹæt/ | หนู |
| expose คำกริยา | /ɪkˈspoʊz/ | เผย, เปิดเผย |
| topic คำนาม | /ˈtɑpɪk/ | หัวข้อ, กระทู้ |
| lesson คำนาม | /ˈlɛs.ən/ | บทเรียน |
| bedroom คำนาม | /ˈbɛdˌɹum/ | ห้องนอน |
กริยาวลีที่คุณจะได้ยิน
| คำศัพท์ | คำอ่าน | ความหมาย |
|---|---|---|
| pick up คำกริยา | ยก, หยิบ | |
| carry out คำกริยา | /ˈkæ.ɹi aʊt/ | กระทำ |
ไวยากรณ์ในวิดีโอนี้
โครงสร้างที่ผู้พูดใช้บ่อยที่สุด พร้อมคำพูดจริงจากวิดีโอ:
| โครงสร้าง | ในวิดีโอ |
|---|---|
| Passive voice be + กริยาช่อง 3 — เน้นสิ่งที่เกิดขึ้น ไม่ใช่ผู้กระทำ | is used · is generated · is connected |
| Relative clauses who / which + อนุประโยค — ข้อมูลเพิ่มเติมเกี่ยวกับคนหรือสิ่งของ | station which is · cables which will · field which will |
| Present perfect have/has + กริยาช่อง 3 — เหตุการณ์ในอดีตที่ยังเกี่ยวข้องกับปัจจุบัน | we've covered · has been · i've shown |
การออกเสียงที่ควรระวัง
ผู้พูดใช้รูปย่อและรูปลดเสียง 21 ครั้ง เช่น we're, I've, we'll ให้พูดแบบสั้นตามที่ได้ยิน
- เสียง “sh” และ “zh”: residential /ˌrɛzɪˈdɛnʃəl/, sheet /ʃit/, potentially /pəˈtɛnʃ(ə)li/, insulation /ˌɪnsəˈleɪʃən/, visualize /ˈvɪʒuəˌlaɪz/
- คำยาว — ลงเสียงหนักให้ถูกพยางค์: electricity /ɪˌlɛkˈtɹɪsɪti/, electrical /ɪˈlɛktɹɪkəl/, residential /ˌrɛzɪˈdɛnʃəl/, manually /ˈmænj(u)əliː/, potentially /pəˈtɛnʃ(ə)li/
เสียงที่คนไทยมักออกเสียงยาก:
- เสียงท้ายคำ — ออกเสียงให้ครบ ไม่เปลี่ยนเป็นตัวสะกดแบบไทย: neutral /ˈnuː.tɹəl/, electrical /ɪˈlɛktɹɪkəl/, coil /kɔɪl/, voltage /ˈvəʊltɪd͡ʒ/, terminal /ˈtɚmɪnəl/
- /v/ — ไม่ใช่ /w/ ให้ฟันบนแตะริมฝีปากล่าง: voltage /ˈvəʊltɪd͡ʒ/, volt /vəʊlt/, invoice /ˈɪnˌvɔɪs/, overload /ˌəʊvəˈləʊd/, screwdriver /ˈskɹuˌdɹaɪvɚ/
- /z/ — เสียงก้อง ไม่ใช่ /s/: residential /ˌrɛzɪˈdɛnʃəl/, expose /ɪkˈspoʊz/, zoom /zuːm/, visualize /ˈvɪʒuəˌlaɪz/
วิธีฝึกกับวิดีโอนี้
- ฟังวิดีโอให้จบหนึ่งรอบโดยยังไม่ต้องพูด แล้วจดคำที่ยังไม่รู้จัก
- เริ่มที่ความเร็ว 0.75× พูดตามทีละประโยค แล้วกลับไปใช้ความเร็วปกติเมื่อเริ่มคล่อง
- อัดเสียงตัวเองแล้วเทียบกับต้นฉบับ โดยสังเกตคำอย่าง wire, neutral, connect เป็นพิเศษ
เทคนิค Shadowing คืออะไร?
Shadowing เป็นเทคนิคการเรียนรู้ภาษาที่ได้รับการรับรองทางวิทยาศาสตร์ พัฒนาขึ้นสำหรับการฝึกนักแปลมืออาชีพ วิธีการนี้เรียบง่ายแต่ทรงพลัง: คุณฟังเสียงภาษาอังกฤษจากเจ้าของภาษาและพูดตามทันที — เหมือนเงาที่ตามผู้พูดด้วยช่วงเวลาห่าง 1-2 วินาที การวิจัยแสดงว่าเทคนิคนี้ปรับปรุงความแม่นยำในการออกเสียง ทำนองเสียง จังหวะ การเชื่อมเสียง การฟังเข้าใจ และความคล่องแคล่วในการพูดได้อย่างมีนัยสำคัญ