Luyện nói tiếng Anh bằng Shadowing qua video: 120V 240V Electricity explained - Split phase 3 wire electrician
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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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Từ vựng và ghi chú luyện nói cho bài học này
Bài luyện nói này dựa trên video “120V 240V Electricity explained - Split phase 3 wire electrician”. Những từ được nhắc lại nhiều nhất trong bài: wire, neutral, bar, breaker, circuit. Video này có 169 câu và 2404 từ để luyện shadowing. Phần lời nói dài 12:10. Người nói nói nhanh, khoảng 198 từ mỗi phút, nên sẽ có nhiều chỗ nối âm và nuốt âm. Chỉ 79% số từ nằm trong 3.000 từ tiếng Anh thông dụng nhất, nên từ vựng khá khó.
Từ vựng quan trọng trong video
15 từ đáng học trong video, kèm phiên âm và nghĩa:
| Từ | Phiên âm | Nghĩa |
|---|---|---|
| wire danh từ | /ˈwaɪɚ/ | dây, dây thép |
| neutral tính từ | /ˈnuː.tɹəl/ | trung lập |
| connect động từ | /kəˈnɛkt/ | nối |
| coil danh từ | /kɔɪl/ | cuộn cảm |
| voltage danh từ | /ˈvəʊltɪd͡ʒ/ | điện áp, hiệu điện thế |
| metre danh từ | /ˈmiːtəɹ/ | mét, thước |
| occur động từ | /əˈkɜː/ | xảy ra |
| terminal danh từ | /ˈtɚmɪnəl/ | nhà ga |
| pipe danh từ | /ˈpaɪp/ | ống sáo, ống tiêu |
| copper danh từ | /ˈkɒpə/ | đồng |
| pole danh từ | /pəʊl/ | cực |
| generate động từ | /ˈd͡ʒɛn.ə.ɹeɪt/ | sinh ra, gây ra |
| grid danh từ | /ɡɹɪd/ | lưới, mạng |
| rat danh từ | /ɹæt/ | chuột |
| topic danh từ | /ˈtɑpɪk/ | chủ đề |
Cụm động từ bạn sẽ nghe
| Từ | Nghĩa |
|---|---|
| check out động từ | tính tiền, trả phòng |
| pick up động từ | nhặt, lượm |
Ngữ pháp trong video
Những cấu trúc người nói dùng nhiều nhất, kèm đúng cụm từ trong video:
| Cấu trúc | Trong video |
|---|---|
| Câu bị động be + quá khứ phân từ — nhấn vào việc xảy ra, không phải người làm | is used · is generated · is connected |
| Mệnh đề quan hệ who / which + mệnh đề — thêm thông tin về người hoặc vật | station which is · cables which will · field which will |
| Thì hiện tại hoàn thành have/has + quá khứ phân từ — việc đã xảy ra nhưng còn liên quan đến hiện tại | we've covered · has been · i've shown |
Phát âm cần chú ý
Người nói dùng 21 dạng rút gọn, ví dụ we're, I've, we'll. Hãy nói theo dạng ngắn đúng như bạn nghe.
- Âm “sh” và “zh”: residential /ˌrɛzɪˈdɛnʃəl/, sheet /ʃit/, potentially /pəˈtɛnʃ(ə)li/, insulation /ˌɪnsəˈleɪʃən/, visualize /ˈvɪʒuəˌlaɪz/
- Từ dài — đặt trọng âm cho đúng: electricity /ɪˌlɛkˈtɹɪsɪti/, electrical /ɪˈlɛktɹɪkəl/, residential /ˌrɛzɪˈdɛnʃəl/, manually /ˈmænj(u)əliː/, potentially /pəˈtɛnʃ(ə)li/
Những âm người Việt thường gặp khó:
- Cụm phụ âm cuối — đọc đủ từng âm, đừng nuốt âm cuối: connect /kəˈnɛkt/, mount /maʊnt/, installed /ɪnˈstɔːld/, component /kəmˈpoʊ.nənt/, underground /ˌʌn.dəɹˈɡɹaʊnd/
- Âm /tʃ/, /dʒ/ và /ʒ/ — tiếng Việt không có, đừng đọc thành “ch” hay “gi”: voltage /ˈvəʊltɪd͡ʒ/, generate /ˈd͡ʒɛn.ə.ɹeɪt/, encourage /ɪnˈkʌɹ.ɪd͡ʒ/, terminology /ˌtɝ.məˈnɑ.lə.d͡ʒi/, visualize /ˈvɪʒuəˌlaɪz/
- Âm /æ/ — mở miệng rộng hơn âm “e”: rat /ɹæt/, manually /ˈmænj(u)əliː/, accidentally /ˌæk.sɪˈdɛnt(ə)li/, magnetic /mæɡˈnɛtɪk/, static /ˈstæt.ɪk/
Cách luyện với video này
- Nghe hết video một lần, chưa cần nói, và ghi lại những từ bạn chưa biết.
- Bắt đầu ở tốc độ 0,75×, nói đuổi từng câu, rồi quay lại tốc độ bình thường khi đã quen.
- Ghi âm giọng mình rồi so với bản gốc, chú ý các từ như wire, neutral, connect.
Phương Pháp Shadowing Là Gì?
Shadowing là kỹ thuật học ngôn ngữ có cơ sở khoa học, ban đầu được phát triển cho chương trình đào tạo phiên dịch viên chuyên nghiệp và được phổ biến rộng rãi bởi nhà đa ngôn ngữ học Dr. Alexander Arguelles. Nguyên lý cốt lõi đơn giản nhưng cực kỳ hiệu quả: bạn nghe tiếng Anh của người bản xứ và lặp lại to ngay lập tức — như một "cái bóng" (shadow) đuổi theo người nói với độ trễ chỉ 1–2 giây. Khác với luyện ngữ pháp hay học từ vựng bị động, Shadowing buộc não bộ và cơ miệng phải đồng thời xử lý và tái tạo ngôn ngữ thực tế. Các nghiên cứu khoa học xác nhận phương pháp này cải thiện đáng kể phát âm, ngữ điệu, nhịp điệu, nối âm, kỹ năng nghe và độ lưu loát khi nói — đặc biệt hiệu quả cho người luyện IELTS Speaking và muốn giao tiếp tiếng Anh tự nhiên như người bản ngữ.