Практика Shadowing: Ohms Law Explained - The basics circuit theory - Изучайте разговорный английский по видео

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Hey there guys, Paul here from theengineeringmindset .com.

In this video we're going to be looking at Ohm's Law

to understand how it works as well as how to use it.

There are also two problems at the end of this video for you to test your knowledge

and see if you can solve.

So what is Ohm's Law?

Ohm's Law is the relationship between voltage, current and resistance and how they relate to each other.

Ohm's law was developed by a German physicist named George Ohm

who undertook many experiments to develop his theory including measuring current by touching live electrical circuits to see how much it hurt.

As you might imagine the higher the current the more it hurt.

Now there are three formulas we need to use for Ohm's law

but we don't actually need to remember these and I'll show you a super easy tip in just a moment.

So the three formulas we use for Ohm's law are voltage equals current multiplied by resistance, current equals voltage divided by resistance,

and resistance equals voltage divided by current.

If that seems like a lot to remember then don't worry because we don't need to remember them.

All we need to remember is Ohm's triangle which looks like this.

So you just need to remember these three letters in order V, I, R.

Then we just write those letters in a triangle with V at the top

and we draw a line to separate the letters.

In fact you don't even need to remember those

because I've made a free PDF guide for you with some worked examples

which you can keep on your PC or your mobile and access wherever you need.

Links for that can be found in the video description down below.

Now all we do when we need to use a formula is cover up the letter we need.

So if we want to find the voltage then we write V equals

and then we cover up the V in the triangle.

That leaves us with I and R so we write I multiplied by which means voltage equals current multiplied by resistance.

You can write a little multiplication symbol in the triangle between the two letters if it helps you.

Now I know what you're thinking, why is current represented with the letter I and not a C for current,

or even a letter A for the unit of ampere?

Well the unit of current is the ampere or the amp, and this is named after André Ampere, a French physicist.

A couple of hundred years ago he undertook lots of experiments many involved varying the amount of electrical current.

So he called this intensity du current or the intensity of current.

So when he published his work they took the letter I and it became standard until this day.

Now you might also come across formulas where the letter E is used instead of V.

The letter E stands for EMF or electromotive force

but don't worry about that just stick to using V

and substitute V for E if you see it used in Ohm's law questions.

Anyway so by covering V we get voltage equals current multiplied by resistance.

If we want to find current then we write down I equals

and then we cover up the letter I in the triangle.

That gives us V and R

so as V is above the R like a fraction

we can write V divided by R therefore current is equal to voltage divided by resistance.

If we want to find resistance then we write down R equals and we cover up R in the triangle.

That leaves us with V and I so we write V divided by I

which gives us resistance equals voltage divided by current.

Let's look at some examples for how to use these formulas.

First let's see how we find voltage and how it relates to the other parts.

Let's say we have a simple electrical circuit with a battery and a resistor.

We don't know what the voltage of the battery is though.

The resistor is three ohms and when we connect a multimeter into the circuit, we see that we get a reading of two amps of current.

We want to find the voltage, so using ohms triangle, we can cover up the V and that gives us V equals I multiplied by R.

We know the current is two amps, so we can write that in, and we know the resistance is three ohms,

so we can write that in also.

Therefore, two amps multiplied by three ohms gives us six volts.

The battery is therefore 6 volts.

Now if you want to check your answers for ohms questions then I've built a free calculator on the website.

You can just drop your numbers in and it will do the calculation for you.

Links for that again in the video description down below.

Coming back to the circuit, if we now double the voltage by connecting two 6 volt batteries in series we get 12 volts.

If we now connect this to the same circuit the current also doubles from 2 amps to 4 amps.

If we double the voltage again to 24 volts, the current will also double to 8 amps.

So what's the relationship here?

We can see that current is therefore directly proportional to voltage.

If we double the voltage, we double the current.

Remember voltage is like pressure, is the pushing force in the circuit.

It pushes the electrons around the wires

and we place things like lamps in the way of these electrons

so that they have to flow through these and that causes the lamp to light up.

By doubling the voltage we see that the current also doubles,

meaning that more electrons are flowing and this occurs as we apply more pressure or more voltage.

This is just like if we were to use a bigger water pump then more water will flow.

Okay, so what about finding current?

Let's say we now have a 3 ohm lamp connected to a 6 volt power supply.

To find the current we write down I equals and then we cover up I in the triangle.

That gives us V divided by R, so current equals voltage divided by resistance.

We know the voltage is 6 volts and the resistance is 3 ohms, so the current is therefore 2 amps.

And that's what we see on the multimeter.

By the way, if you don't have a multimeter then I highly recommend you get one.

It's essential for troubleshooting but also building your essential electrical knowledge.

I'll leave some links down below for which one to get and from where.

So we saw what happens when we use a resistance of 3 ohms in the circuit.

But if we double the resistance to 6 ohms by placing another 3 ohm lamp into the circuit, the current halves to just 1 amp.

If we double the resistance again to 12 ohms, the current will half again to 0 .5 amps.

We can visually see this because the lamps will become less bright as the current reduces from the increase in resistance.

So what's the relationship here?

We can see that the current is inversely proportional to the resistance.

When we double the resistance the current will decrease by half.

If we half the resistance the current will double.

Current is the flow of electrons or the flow of free electrons.

For us to make this lamp shine we need to push electrons through it.

How do we do that?

We apply a voltage across the two ends.

The voltage will push the electrons.

The atoms inside the copper wire have free electrons in their valence shell

which means they can very easily move to other copper atoms.

They will naturally move to other atoms by themselves

but this will be in random directions which is of no use to us.

100

For the lamp to turn on we need lots of electrons to flow in the same direction.

101

When we connect to voltage source

102

we use the pressure of the battery to push the electrons through the circuit all in the same direction.

103

For example to power this 1 .5 ohm resistive lamp with a 1 .5 volt battery requires 1 amp of current.

104

This is equal to 6 ,242 ,000 ,000 electrons passing from the battery

105

and through the lamp every second and if we can achieve this then the lamp will stay at full brightness.

106

If the voltage or current reduces or the resistance of the circuit increases then the lamp will become dimmer.

107

Okay now let's look at finding resistance.

108

Say we have a resistive lamp connected to a 12 volt power supply.

109

We don't know how much resistance is adding to the circuit but we measure the current at 0 .5 amps.

110

To find the resistance we write down R equals and and then we cover up the R in the triangle.

111

We're left with V and I, so resistance equals voltage divided by current.

112

We know the voltage is 12 volts and the current is 0 .5 amps, so 12 divided by 0 .5 gives us 24 ohms of resistance.

113

Resistance is the opposition to the flow of electrons.

114

It tries to prevent electrons from flowing.

115

That's why we use resistors in circuits to reduce the current and protect components such as an LED.

116

If we try to connect an LED directly to a 9V battery, it will blow out because the voltage and the current are too high.

117

But when we add a resistor into the circuit, then these are reduced, so the LED is protected and will shine brightly.

118

So given the circuit, we can increase the current by increasing the voltage, or we can also increase the current by reducing the resistance.

119

We can also reduce the current by increasing the resistance.

120

Okay, time for you to test your skills.

121

Can you solve these problems?

122

I'll leave a link for the answer and the solution in the video description down below.

123

Problem one, let's say we have this lamp which has a resistance of 240 ohms.

124

If we plug this into an outlet in the US which uses 120 volts, what will the current be?

125

Problem two, if I plug the same 240 ohm resistive lamp into an outlet in the UK, we get a current of 0 .958 amps.

126

So what is the voltage being applied here?

127

Okay guys, that's it for this video, but to continue your learning,

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then check out one of the videos on screen now and I'll catch you there for the next lesson.

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Don't forget to follow us on Facebook, Twitter, Instagram, LinkedIn, as well as theengineeringmindset .com.

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Лексика и советы по произношению к этому уроку

Этот урок разговорной практики построен на видео «Ohms Law Explained - The basics circuit theory». Чаще всего повторяются слова: current, voltage, resistance, Amp, lamp. В этом видео 108 предложений и 1796 слов для шедоуинга. Речь длится 9:49. Говорящий говорит быстро, около 183 слов в минуту, поэтому звуки часто сливаются и сокращаются. Только 80% слов входят в 3000 самых частых слов английского языка, поэтому лексика сложная.

Ключевая лексика этого видео

15 слов из видео, которые стоит выучить, с произношением и значением:

Слово	Произношение	Значение
voltage существительное	/ˈvəʊltɪd͡ʒ/	напряже́ние, вольта́ж
circuit существительное	/ˈsɝ.kɪt/	кругооборо́т, цикл
lamp существительное	/ˈlæ̝mp/	ла́мпа, ла́мпочка
divide глагол	/dɪˈvaɪd/	дели́ть, разделя́ть
triangle существительное	/ˈtɹaɪˌæŋɡəl/	треуго́льник
connect глагол	/kəˈnɛkt/	свя́зывать, связа́ть
litter существительное	/ˈlɪt.ɚ/	подсти́лка
formula существительное	/ˈfɔː.mjʊ.lə/	фо́рмула
metre существительное	/ˈmiːtəɹ/	метр
atom существительное	/ˈætəm/	а́том
wire существительное	/ˈwaɪɚ/	про́волока, про́вод
solve глагол	/sɒlv/	реша́ть, реши́ть
experiment существительное	/ɪkˈspɛɹ.ə.mənt/	экспериме́нт, о́пыт
copper существительное	/ˈkɒpə/	медь
leaf существительное	/lif/	лист, ли́стья

Фразовые глаголы, которые вы услышите

Слово	Значение
write down глагол	запи́сывать, записа́ть
blow out глагол	задуть
check out глагол	проверя́ть, прове́рить
light up глагол	свети́ть, освети́ть

Грамматика в этом видео

Конструкции, которые говорящий использует чаще всего, с точными словами из видео:

Конструкция	В видео
Пассивный залог be + причастие прошедшего времени — важно, что происходит, а не кто это делает	was developed · can be found · is named
Present Perfect have/has + причастие прошедшего времени — прошлое действие, важное сейчас	I've made · I've built
Придаточные определительные who / which + предложение — уточнение о человеке или предмете	directions which is · lamp which has

Произношение, на которое стоит обратить внимание

Говорящий использует 16 сокращённых и редуцированных форм, например don't, I'll, I've. Произносите их коротко, так, как слышите.

Звуки «sh» и «zh»: shine /ʃaɪn/, shell /ʃɛl/, fraction /ˈfɹæk.ʃən/, calculation /ˌkælkjuˈleɪʃn̩/, multiplication /ˌmʌltɪplɪˈkeɪʃən/
Длинные слова — следите за ударением: electrical /ɪˈlɛktɹɪkəl/, experiment /ɪkˈspɛɹ.ə.mənt/, naturally /ˈnæt͡ʃ.(ə.)ɹə.li/, intensity /ɪnˈtɛnsɪti/, visually /ˈvɪzju.əli/

Звуки, трудные для русскоязычных:

/w/ — губы округлены, это не /v/: wire /ˈwaɪɚ/, wherever /(h)wɛɹˈɛvɚ/
Звонкие согласные в конце слова — не оглушайте их: voltage /ˈvəʊltɪd͡ʒ/, divide /dɪˈvaɪd/, solve /sɒlv/, plug /plʌɡ/

Как заниматься с этим видео

Прослушайте всё видео один раз молча и выпишите незнакомые слова.
Начните со скорости 0,75×, повторяйте предложение за предложением и вернитесь к обычной скорости, когда станет легко.
Запишите себя и сравните с оригиналом, обращая внимание на такие слова, как voltage, circuit, lamp.

Что такое техника Shadowing?

Shadowing — это научно обоснованная техника изучения языка, изначально разработанная для подготовки профессиональных переводчиков и популяризированная полиглотом доктором Александром Аргуэльесом. Метод прост, но эффективен: вы слушаете аудио на английском от носителей языка и немедленно повторяете вслух — как тень, следующая за говорящим с задержкой в 1–2 секунды. В отличие от пассивного прослушивания или грамматических упражнений, Shadowing заставляет мозг и мышцы рта одновременно обрабатывать и воспроизводить реальные речевые паттерны. Исследования показывают, что это значительно улучшает точность произношения, интонацию, ритм, связную речь, понимание на слух и беглость речи — что делает его одним из самых эффективных методов для подготовки к IELTS Speaking и реального общения на английском.

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