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• 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.

• It is quite dangerous.

• Fine.

• 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?

• 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.

• 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.