Placeholder Image

Subtitles section Play video

  • Smart Learning for All.

  • Topic: Electric Charge.

  • How does a plastic comb attract paper?

  • What?

  • You don't believe me?

  • Ok.

  • Let us try.

  • Take a plastic comb and bring it close to some pieces of paper.

  • Hey, Wait.

  • Don't laugh.

  • We need to do something first.

  • Rub the comb on your dry hair and then bring the comb close to the pieces of paper.

  • See, I was correct.

  • The pieces of paper got attracted to the plastic comb.

  • Do you think it is magic?

  • No, the reason behind this is electric charge.

  • Electric charge is the quantity of electricity held in an object.

  • There are 2 types of electric charges, positive and negative.

  • However, there are some objects where the positive and negative charges are equal to one another.

  • In such cases, we say that the object is electrically neutral.

  • So, was the plastic comb initially electrically neutral or electrically charged?

  • Initially, the plastic comb was electrically neutral.

  • That means it had equal number of positive and negative charges.

  • Hence, it did not have the ability to exert a force and attract the pieces of paper.

  • So, after rubbing the plastic comb on our dry hair, why was it able to attract the pieces of paper?

  • I will tell you why.

  • When we rubbed the plastic comb on our dry hair, it gained an electric charge.

  • Once it got electrically charged, it got the ability to exert a force on the pieces of paper and attract them.

  • This charge is called as static electricity.

  • However, do you think, like a plastic comb, a metallic comb will also attract the pieces of paper?

  • No, you are wrong.

  • A metallic comb will not attract the pieces of paper like the plastic comb.

  • Wondering why is that so?

  • It is because plastic is not a good conductor of electricity.

  • It does not allow the electric charges to flow through it onto the earth.

  • As a result, the charges build in the plastic comb.

  • Making it electrically charged and enabling it to attract the pieces of paper.

  • However, metal is a good conductor of electricity.

  • It does not let the charges build in it.

  • It allows the electric charges to flow through it onto the earth.

  • Thus, not allowing the metallic comb to get electrically charged.

  • As a result, the metallic comb does not attract the pieces of paper.

  • Topic: Neutralization Reaction.

  • How to treat a bee sting?

  • Hey. Hold On.

  • Don't go near that honeycomb.

  • Please listen to me.

  • It is quite dangerous.

  • Fine.

  • Go ahead.

  • See, I told you.

  • Ok.

  • Now, don't worry.

  • Put this baking soda solution on the bee stung area.

  • You got some relief, right?

  • Do you know why you got relief?

  • This happened because a neutralization reaction took place when we applied baking soda on the stung area.

  • The venom of a honey bee contains formic acid.

  • When it stings us, it injects that acid into our skin.

  • Formic acid causes immense pain and irritation.

  • However, when we apply baking soda solution, which is a mild base, on the stung area.

  • It neutralizes the formic acid and cancels its effect.

  • As a result, the sensation of pain and irritation decreases and we get some relief.

  • Such a reaction between an acid and a base is called neutralization.

  • In neutralization, both acidic and basic solutions neutralize the effect of each other.

  • The nature of both acids and bases gets destroyed.

  • Hey, Wait. What are you doing?

  • Don't tease that insect.

  • It is not a honey bee.

  • It looks similar to a honey bee but it is a bit longer.

  • It is called a wasp.

  • At least this time listen to me.

  • Ok.

  • Don't listen and bear the consequences.

  • Applying the baking soda is not going to help.

  • See, nothing is happening.

  • I will tell you what to do.

  • Pour this vinegar on the stung area, you will get some relief.

  • Why do you think the baking soda solution did not help in this case?

  • Earlier, in case of the honey bee, we learnt that its venom is acidic.

  • Hence, baking soda, being a basic solution helped to neutralize the effect

  • Now, in case of a wasp, the nature of its venom is basic.

  • When it stings us, it injects that venom into our skin.

  • This venom causes us pain and itching.

  • Now, baking soda is also a basic solution.

  • Hence, it will not provide any sort of relief.

  • However, when we pour vinegar, which is a mild acid, on the stung area.

  • The acid, that is, vinegar and the base, that is, the wasp's venom get neutralized.

  • As a result, the sensation of pain and itching decreases and we feel better.

  • Topic: Nuclear fusion.

  • Why is nuclear fusion not used to generate electricity?

  • You really want to know the answer to this, right?

  • But wait.

  • Before answering the question, let us understand what is meant by nuclear fusion.

  • When two lighter nuclei combine to form a heavy nucleus, a large amount of energy is released.

  • This process is called nuclear fusion.

  • Where does this nuclear fusion take place?

  • You think that it takes place in a laboratory?

  • No, you are absolutely wrong.

  • Nuclear fusion takes place in the sun.

  • The nuclei of two hydrogen atoms join together to form a heavy nucleus of helium with the release of a large amount of energy.

  • How do you think this energy reaches us?

  • No.

  • It does not reach us through power lines.

  • Wait I will tell you.

  • The energy released after nuclear fusion reaches us in the form of sunlight, ultraviolet radiations, heat, etc.

  • Hey.

  • But we are already producing electricity with the help of nuclear fission.

  • So, why do we require nuclear fusion?

  • For this, you need to first understand the difference between nuclear fusion and nuclear fission.

  • As we already know, nuclear fusion is the fusion of two lighter nuclei.

  • With the release of a large amount of energy.

  • The exact opposite process happens in nuclear fission.

  • Here, a heavier nucleus splits into two lighter nuclei, releasing a large amount of energy.

  • This process of fission is used in nuclear power plants.

  • Where a heavy nucleus of uranium is split into lighter nuclei.

  • The energy that is released in this is used to generate electricity.

  • However, there is a major disadvantage of nuclear fission.

  • Wondering what it is?

  • The major disadvantage is that uranium is a radioactive element.

  • When uranium undergoes fission, it generates radioactive waste along with energy.

  • This radioactive waste is very harmful for most lifeforms and the environment.

  • Hence, we need to find a clean and safe source of energy to generate electricity.

  • What source would that be?

  • Would it be nuclear fusion?

  • You are right.

  • Then why are we not harnessing the energy of nuclear fusion to produce electricity?

  • This is because, for nuclear fusion, two conditions are required.

  • They are high pressure and high temperature.

  • Only when these conditions are met, can the two nuclei travel at very high speeds resulting in collision.

  • On earth, it is extremely difficult to create such high pressure and temperature.

  • Even if we are somehow able to create these conditions, the question is how will we control them?

  • As there are many questions unanswered and unsolved.

  • We have not yet succeeded in using nuclear fusion in the production of electricity.

  • Topic: Sound.

  • Why do we hear echoes?

  • Hey. Hold On.

  • Don't go into that room.

  • You don't want to listen to me.

  • Ok.

  • Then go ahead.

  • See, I warned you.

  • Will you listen to me now?

  • Don't worry.

  • The sound you heard was just an echo of your voice.

  • Let me explain what an echo is.

  • When we speak or laugh in a big empty hall, we hear our own sound repeatedly.

  • This is because our sound waves get reflected from the walls of the hall back to us.

  • The reflected sound that we hear is called an echo.

  • Hence, an echo is defined as the repetition of sound.

  • Caused by the reflection of sound waves from a hard surface back to the listener.

  • Hey. What are you doing?

  • Are you trying to hear an echo?

  • It is not that easy.

  • There are 2 ideal conditions for an echo to be heard.

  • When we speak or laugh, we hear our original sound at that moment.

  • The sensation of this original sound remains in our brain till 0.1 seconds.

  • This time is called the persistence of hearing.

  • When we utter sounds, some of our sound waves get reflected while some get absorbed.

  • If the reflected sound waves reach our ears before the completion of 0.1 seconds.

  • Then our brain does not perceive the original and reflected sounds as separate sounds.

  • They are interpreted as one sound, therefore, in order to hear two distinct sounds or an echo.

  • The time gap between the original sound and the reflected sound or echo should be at least 0.1 seconds.

  • This is the first condition for an echo to be heard.

  • Do you know when the time gap will be more than 0.1 seconds?

  • This gets us to the second condition for an echo.

  • The minimum distance between the speaker and the reflecting surface should be at least 17.2 meters.

  • When the distance is 17.2 meters and we start speaking.

  • Assume that the original sound reaches our ears at this time and the reflected sound reaches our ears at this time.

  • Then the time interval between the reflected sound and the original sound will be equal to 0.1 seconds.

  • As a result, we will be able to hear an echo.

  • Alright.

  • Now, let us try and hear an echo in this room?

  • It is even bigger than the previous room.

  • Now, why can't we hear an echo?

  • This is because there are many soft furnishings like sofas, carpets, curtains, etc., in this room.

  • They absorb most of the sound waves.

  • As the sound waves do not get reflected, we are not able to hear an echo in this room.

  • Hence, one more thing to consider, if we want to hear an echo.

  • Is that there should be minimal use of such sound absorbing materials.

  • Topic: Ear.

  • How do ears help with balancing?

  • They really do.

  • You don't believe me.

  • Ok. Can you play a guitar and walk at the same time?

  • How do you think you are able to maintain your balance?

  • Do you know why you can't balance yourself anymore?

  • Wait, I will tell you.

  • This happens because there is a connection between our ears and body balance.

  • Our ear consists of 3 parts, outer ear, middle ear and inner ear.

  • Our inner ear works in sync with our eyes and muscles.

  • Helping us maintain balance, while we are doing various activities.

  • The inner ear consists of three semicircular canals.

  • Called superior semicircular canal, posterior semicircular canal and lateral semicircular canal.

  • The three semicircular canals are arranged in three different positions.

  • Each of these canals has a fluid called endolymph and hair cells called cilia at the base.

  • Whenever we move our head, the fluid moves, resulting in the movement of the cilia as well.

  • When the cilia moves.

  • It sends signals to the brain informing which direction our head has just moved in.

  • Each canal has different functions as per the movement of our head.

  • When we move our head up and down.

  • The superior semicircular canal helps our brain to understand the yes motion.

  • When we tilt our head towards our shoulders.

  • The posterior semicircular canal helps our brain to understand the tilting motion.

  • When we move our head from side to side.

  • The lateral semicircular canal helps our brain to understand the no motion.

  • It was too complicated, right?

  • Ok, don't worry about it.

  • Relax.

  • Why don't you go on a merry go round ride?

  • Hey.

  • Why were you not able to maintain your balance?

  • This is because when you sat in the merry go round and started rotating.

  • The fluid in the semicircular canals also started to move.

  • After a while, it was moving at the same rate at which you were moving.

  • However, when the ride stopped and you got down from the ride, the fluid was still in motion due to inertia.

  • Hence, even though you were not moving.

  • The moving fluid gave your brain false information telling you that you are still in motion.

  • Thus, you were not able to maintain your balance.

  • Topic: Rancidity.

  • Why is a bag of chips half full?

  • Looks like you don't believe me.

  • Open the bag.

  • See I told you.

  • The bag of chips is indeed half full.

  • Why is that so?

  • It is mainly because of a concept called rancidity.

  • When food becomes rancid, it develops an unpleasant smell and taste and it becomes unsafe for consumption.

  • Rancidity generally refers to a condition.

  • Where the fats and oils present in food get oxidized, resulting in food spoilage.

  • Since the chips contain fats and oils, they are likely to get rancid.

  • Therefore, to prevent this, nitrogen gas is flushed into bags of chips by manufacturers.

  • But, why nitrogen?

  • Nitrogen does not react with fats and oils.

  • As a result, rancidity does not take place.

  • Moreover, a gas in the bag serves as a cushioning agent and prevents the chips from crumbling.

  • That is why the bag of chips is only filled till half.

  • Topic: Concave Mirror.