Important Dimensional formulas | NEET | JEE MAINS |

追加: 2026-05-20

[00:00:01]Okay.

[00:00:06]So I told you that any dimensional formula if it is represented with mass, length, time, temperature, theta, electric current, a r i number of moles is repent with m letter h completely one word m represents. Okay. So now just see here first thing is if you consider velocity, velocity means displacement time. basic formula which you have learned in lower classes that is velocity is nothing but displacement by time displacement at a length and time is t okay so now I am writing L by D now this T goes to numerator become L t power minus one okay so this is the dimensional formula for velocity but I told you that you have to represent with mass length and time mass also should be present in the dimensional formula that's why mass is not there so I'll write m^ 0 okay velocity so if you are going to consider volume of a cubid is nothing but length into bread to height.

[00:00:57]So all the three are lengths only. So we can write this as LQ more length length.

[00:01:01]So we can write it as LQ. But here also 4x3 is not having any dimensional formula. It is a constant only radius is having dimensional formula. Radius is also nothing but length here. So that also we write it as L cq. So what is the dimensional formula for volume? M is not present. So 0 L is present and T is not present. So only L is present. So M^ 0 T0 L LQ be right, isn't it? Okay. So this is one formula for volume. Next, if you consider area, area means area of a circle if you consider it is going to be p<unk> r². And if it is a cube, we write it as side square. Okay? And a square we write it as understood. So pi does not have a dimensional formula. So area of a cube means side square. Side square h and area of a circle is p<unk> r². So therefore radius is also length we write it as l². And here also side square is written as L square. Mass is not present. Time is not present. That's why the dimensional formula of area can written as m^ 0 L² E power 0. This is the dimensional formula for area, dimensional formula for volume, dimensional formula for velocity. Okay.

[00:02:08]So dimensional formula for velocity. Now what is the dimensional formula for acceleration? See acceleration is nothing but change in velocity by time.

[00:02:17]What is what is the formula for acceleration? Change in velocity by time. So v byt we write and you know velocity can also be written as displacement by time whole divided by time. So therefore acceleration is nothing but if t comes to numerator becomes t² okay so therefore we can write this acceleration as l and in the denominator it is taken as t². So a can be written as what is this lt power minus2 mass is not present so m^0 l power minus2 like this we write. So general formula is converted into dimensional formula. The next important formula is what is momentum? What is momentum? See momentum is nothing but mass into velocity.

[00:02:57]Momentum means mass interval. Don't don't bother about writing the notes.

[00:03:00]Okay? See all these notes will be sent to your WhatsApp numbers. This video also will be sent.

[00:03:14]physics problem just concentrate on the board no need to write anything 100% concentrate on the board formula how how I'm converting ordinary formula into dimensional formula shala important this is the basic of your physics so concentrate exactly on the board I'm also cool and creative I'll try to explain from basics so that you need not by heart any dimensional formula you need not by any dimensional formula because in that pressure of your niche exam only understood. So that's why don't by heart anything. So momentum h what is the meaning of momentum? Momentum is given by letter v. It is a product of mass into velocity. It's a product of mass into velocity. So mass I'm writing it as m and I told you velocity is nothing but displacement by time. So this can be written as lt power minus one. So ml power minus one is going to be the dimensional formula for momentum. Hope you understand you know. So this is going to be the dimensional formula for momentum. Next if it is over what is the dimensional formula for force. See no dimensional formula I'm barting now because I'm weak at hearting and I will make you not to have any dimensional formula. You will derive on the spot by using your basic knowledge you'll derive on the spot. So see here now. So what is the force here actually? See force is nothing but mass into acceleration. So therefore force is equal to mass into acceleration. Acceleration is nothing but change in velocity by time and velocity is nothing but displacement by time by time. So acceleration is nothing but L by T² S by T² where S is L and this is going to be T². So acceleration dimensional formula is LT power minus2.

[00:04:52]Okay. So mass you write it as M and acceleration you write it as L powerus 2. This is a dimensional formula for force. Next what is the dimensional formula for work? What is the dimensional formula for work? You know work is nothing but force into displacement. Force into displacement. W is equal to force means mass into acceleration into displacement. So W is equal to mass means capital M.

[00:05:14]Acceleration into change in velocity by time. Velocity means displacement by time by time. So A is nothing but S by T². A is nothing but L by T². Therefore M A is nothing but L power of minus2. So LT power of minus2 into L. So therefore w is nothing but ml² t^ minus2 is the dimensional formula for what? Then what is the dimensional formula for kinetic energy? Kinetic energy is nothing but half mv² and half does not have any dimension. And velocity I told you it is displacement by time which is length by time. So v is equal to lt power minus1.

[00:05:49]T go to numerator become t power minus one. Half is a number. Number does not have a dimension. So kinetic energy is nothing but m okay capital m and velocity is lt power minus1 square.

[00:06:01]Therefore kinetic energy dimensional formula is ml² t power minus2. Then what is the dimensional formula for potential energy? Okay. So potential energy means what? If you raise a body from bottom to top okay so displacement will become height. Displacement in the upper direction is going to become height. And force applied on the body which is lifted upwards is force due to gravity which is mg. And you know work done is nothing but force due to gravity into displacement. So therefore force due to gravity means m into g. Generally force formula is m into a. But whenever acceleration due to gravity acts the formula will change which is taken as m into g which is also called as weight.

[00:06:38]Okay. M into g. Then what is what is the formula for potential energy? See potential energy work. So this is force due to gravity at mg and displacement in upward direction is taken as h. So therefore potential energy formula is mg into h see acceleration and acceleration due to gravity and formula same okay formula is going to be l power -2 so therefore potential energy formula is going to be m you write as it is g means l power minus2 and h is nothing but l so the dimensional formula for potential energy is ml² t power minus2 is it okay so after that h some tough physical quantities. Okay, tough physical quantities if you observe. See here. So, so these physical quantities are a little bit tough to remember. See how we have to derive this. I'll explain the concept also and dimensional formula so that it will be very easy for you to understand here. Okay. So, what is going to happen now? Just see.

[00:07:40]Okay.

[00:07:41]So, here for the dimensional formulas where students try to buy hard but they cannot buy hard they'll forget them.

[00:07:49]Okay. So first of all, what is the dimensional formula for charge? You know, current is nothing but rate of flow of charge or charge by time. This is a basic formula you know in 10th class also. Okay. But what is the dimensional formula for charge? Charge can be taken as I into T. I means current here. And I told you current is represented with letter A and this is T.

[00:08:08]Okay. So therefore charge is nothing but A into T. What is the dimensional formula for charge? Just A D. Okay. Hope you are understanding what I'm saying because I told you in the first slide only that mass is represent m length time t theta r k and electric current a r i a means ampere okay and the number of moles is represent m okay so like this here um yes so what is the dimensional formula for charge means a into t so if you keep like that if you want to keep like that or if you want to represent whole dimensional formula. M is not present. L is not present. Okay. So, T is present and A is present. Understand what I'm saying?

[00:08:54]Okay. So, this is a dimensional formula that is dimensional formula is going to be a then what is the dimensional formula for permitivity of free space?

[00:09:04]What is the dimensional formula for permitivity of a free space? So to understand the permitivity, let us go to a little bit basic concept here of permitivity here.

[00:09:13]So permitivity easy to remember you know. Okay. So what is this permitivity? So you know force is nothing but Q1 Q2 by 4 pi epsilon into R². Okay. So this is the formula which is present in your electrostatics electric charges and fields in second year or in your lower classes also. When these two when two charges are present okay there is Q1 and Q2 and they are having distance R. Okay. So force is directly proportional to product of the charges. Force is inversely proportional to square of the distance between them is called as pulum's square law. Inverse square law. Understood. What is the meaning of this? Charge strong attraction strong repulsion strong. Here same charges will repel. If this is negative and this is positive here and the distance is there they are having a force of attraction. Here they are having a force of repulsion. Either it is a force of repulsion or attraction.

[00:10:06]Pulum's inverse square will be the basic formula and charges are strong means force is strong and when the distance increases force decreases distance if you combine these two you'll get a formula which is directly proportional to Q1 Q2 by R² and F is equal to proportional if you remove you'll get a constant K q1 Q2 by R² K is nothing but 1x 4 pie okay so F is equal to K means you'll write 1x 4 pi epsilon KN and this is going to be Q1 Q2 by R2.

[00:10:44]Okay. Now see what is this permitivity here. These two charges you are keeping in air or vacuum H air or vacuum. See epsilon not is called as permitivity.

[00:11:01]Okay. So what is the meaning of permitivity? When two charges are kept in a vacuum area, okay, they are repelled and if they are opposite charges, they are opposite charges, they are going to attract. You know about this, isn't it?

[00:11:17]But force of attraction or repulsion depends upon the medium. Whatever the medium you consider that is either allowing attraction or slightly allowing attraction or does not allow attraction depends upon the medium. Okay. So what is permitivity here? For example, this is free space or air. So force in air is taken as 1x 4 pi epsilon q1 q2 by r² where epsilon is nothing but permitivity of medium. Permitivity I'm telling what is the meaning name itself says that ability to permit traction or repulsion.

[00:11:49]Isn't it? See permitivity is not the property of the charges. Permitivity is the property of the medium. I'll give an example in Kore not such a highly western culture in Kore as soon as a college is left all girls will go aside first of all they'll be left and boys will go aside right let because our medium our surrounding our environment does not allow one boy one girl going beside and talking together they having boyfriend and girlfriend first time I went to hydroat in arangad teaching in a college which is the name is ratnam junior college ratna junior college there I went first time in from kernel to hydroat to teach As soon as the class is over, one boy, one girl are moving outside. In class also they are talking to each other, writing something and giving the slips to the girls and boys are giving girls, girls are writing the reply and giving outside. What is this nonsense you're doing in the class?

[00:12:36]Get lost from my class. He said the complaint principal principal called me.

[00:12:40]Sir, you are coming from very old background. There is an old place in Carl where boys does not allow, girls are not allowed by the parents but this is not here our sir. See why full strength is there? Because co-education no boy will be absent because girls are regularly coming. Boys also regularly coming attendance is full. Okay. Sir please don't scold the girls and boys because we have admissions because we are allowing them to communicate with each other with each other and increase their knowledge. All right or not? So that is the that means medium is allowing their that's that medium environment is like that is not I have seen I was I was shocked one girl is introducing boyfriends with his father.

[00:13:17]Father, dad, you know these are my friends. Raju, Ravi, this fellow is Shiva. They are very close friends. We read together. Father is telling see my my daughter is very lazy. You do come and study.

[00:13:32]He's telling I saw if a dad says to a boy understand our medium does not allow. So epsilon KN is not the property of the charges it is the property of the surroundings. So how are you going to find out the dimensional formula for epsilon not? For that what you have to do is constants you have to remove.

[00:14:06]Constants you have to remove. Therefore epsilon is nothing but q1 q2 by f comes to denominator f into r². I told you that I is nothing but q byt. Q is nothing but i into t. Q is nothing but a into t is the dimensional formula for charge. So therefore epsilon not means what will you write? Okay. So epsilon not means Okay, see just now. So now Q means A into T is the dimension of M is ampere.

[00:14:37]So we can write A into T A into T A² P².

[00:14:41]Force I told you just now force is nothing but mass into acceleration. Mass means M. Acceleration is nothing but L power minus 2. So m L pus2 radius means we write it as L². So what is the dimensional formula for permitivity?

[00:14:54]Okay. So mass is there here mass comes to numerator m^us 1. So l² lq lq comes to numerator become lus 3 + 3. Okay.

[00:15:06]Then what else here time t powerus 2 comes to numerator becomes t +2 already +2 is present. So t power 4 is it?

[00:15:16]So t power 4 a is already present. Okay.

[00:15:19]So the dimension formula for you can't remember this one. How will you do this one then? So very fast because after practicing so many times you write f= 1x4 by epsilon q1 q2 q² directly by r². Okay. Dimensions Q² by F into R square. Q square is nothing but Q² F - 2 L². Okay. Ready? Your formula is ready. What is that? Mus Lus 3 Tus T² T² already present T 4. Okay. What is this now? M L powerus T 4 and A². Ready? Your formula is ready. Understand? Because practicing understood. So this is the dimensional formula for what?

[00:16:17]Okay, epsilon KN. Okay, then what is the dimensional formula for electric field?

[00:16:24]Electric field transa difficult how to remember that one but there is one basic logic. See these formulas which I have written here will give you a simple idea how to derive the formula formulas formula.

[00:16:37]So what is electric field? See one plus point in this chapter is when I'm explaining electric field I will revise that chapter also here don't dimension but because I revising all the chapters because this is this chapter is the combination of all the chapters so let's see now so what is the dimensional formula for electric field now electric field dimensional formula so what I'm going to do now let us go to the basic discussion of what is electric field so what is the positive charge here this is a positive charge charge.

[00:17:09]See positive charge is having certain space certain space surrounding it and that is called as electric field. This is called as electric field and that is called as a this is called as space of influence. Space of influence.

[00:17:52]So what is electric field? The space or region served in the charge within which its influence can be felt. Electric field means the space the space or the region surrounding the charge within which its influence can be felt beyond that there is no influence to local it will attract opposite poles repel sorry opposite poles attract opposite charges will attract same charges will repel am I or not father loves daughter mother loves son it's law of nature understood that's it okay so that happening So what are we going to do now? How do you find out electric field?

[00:18:32]Now see if you want to find out electric field intensity. Okay. What is the topic which I want to explain here is electric field intensity. Electric field I explained just now. What is the meaning of electric field intensity?

[00:18:51]Sun is having high intensity today. It is burning our ass.

[00:18:57]meaning okay now let's see electric field intensity means what intensity means point electric field what is electric field intensity at that point if you want to find out if you want to find electric field at that point what you have to do what you have to do I'll give a small example for so I told that I have got lot of intensity then if you go here what I'll do if you want to find out intensity at that point not keep one positive charge test charge test.

[00:19:58]So if this is a charge Q I'll keep one test charge Q not at that place. So electric field intensity is nothing but force acting on unit charge. If you keep a unit charge at that place, how much force that unit charge will experience?

[00:20:11]That will be the intensity a point.

[00:20:31]Thench.

[00:21:08]So, so what is there now? Electric force acting on unit charge very simple here.

[00:21:13]So how much simple it is now? How to find out the dimensional formula? Now this is force means you know mass into acceleration ml power minus2 charge means a into t just now I told you so how easy it is m l t power minus 3 okay t comes to numerator t^ -1 so t^ -2 - -3 and a power minus one this is going to be the dimensional formula for electric field intensity okay so what is the dimens next dimensional formula here so what is the next dimensional formula okay so how to find out the dimensional formula for electric potential L H I am explaining so detail because you have got a revision of that chapter also electrostatics revision. So how to find out the electric potential. Now easy to remember the formula also electric potential means what you know any charge is having certain space or region which is called as what is this region called as electric field and you want to find out what is electric potential at this place. potential. See potential is an English word. Gandhi G is having very great potentialities. Highly talented person.

[00:22:19]He motivated the whole India.

[00:22:21]Highly potential. Potential mean store energy. So here also what is the potential at that place? H as this is having electric field. What is the potential at that place?

[00:22:34]And he does not want to go to school.

[00:22:36]Okay. But every day his or her mother will hold him from his house. His house is present at infinity test because he is having a great potentialities not to go to school. So what is his potentiality?

[00:23:08]Okay.

[00:23:15]And then so so that is called as potential. So what is the potential?

[00:23:18]Actually electric potential is nothing but work done on unit charge to bring this unit charge from infinity to that point.

[00:23:45]So, electric potential is nothing but work done on unit charge. It's very easy. Now work done means you know force into displacement force mass into acceleration displacement mass acceleration is LT power minus2 displacement is L. So work done means M L² T power minus2 charge means A into T.

[00:24:02]So electric potential is nothing but ml² t minus 1 this is tus 2 is going to be a powerus so easy to remember electric so that you can remember the formula and funny things we'll remember tragedy we forget we don't like tragedy Funny things extra.

[00:24:31]So funny things will make you to for long-term memory. You have to associate funny things with your subject so that you can remember for longer time. This is not what time waste. Okay. So every example I'm giving you so that your memory becomes strong. Hope you understand now. So that is the formula for electric potential. Is it okay? Huh?

[00:24:49]So if that is the formula for electric potential then what is the formula for capacitors?

[00:24:54]What is the formula for capacitors? See capacitor capacitor is one device just remember okay capacitor is one device which can store the charge temporarily.

[00:25:06]Our cell phone is a temporary storage device. It is not a power source. You have to take this this cell and keep for charging for 1 hour then 24 hours it will work for you. Isn't it? So this having a temporary storage device in that batter is having capacitors. Let us imagine capacitor mean they will store the charge temporarily and they will distribute the charge for one day. So capacitor is a temporary storage device.

[00:25:28]You have to remember that one capacitor is a capacity to store Remember, take this gift for you.

[00:26:19]Next she is now doing completed her engineering. So that is the meaning of encouragement.

[00:26:28]You have to appreciate for that hormones neurons you should not discourage.

[00:26:37]Nobody will discuss in this institute for you because we are all so that should be the challenge even though if you are okay so don't think that I got 300 marks I got 400 marks I got 500 marks no how many marks you got is not important how much you are going to get is important understood or not so Now just see uh this is a capacitor which is having capacitor C and this is the potential here and from this battery it will take positive charge from positive terminal it will take negative charge from negative terminal. Okay. So here the charge on the capacitor is directly proportional to potential supplied. The greater the potential you supply the greater will be the charge on the capacitor. Charge is directly proportional to potential applied. So Q is nothing but C into V.

[00:27:33]Okay. So what is C here? Now C is nothing but Q by V. This is the basic formula for capacitors. Hope you're understanding what is the meaning of capacitance. Is it okay? So, but I have to find out what is the dimensional formula for capacitance. So, what is the dimensional formula for capacitance?

[00:27:45]Now, just see here I just told you that charge on the capacitor is directly proportional to potential. Q is equal to CV. C is equal to Q by V. Okay. So, okay. So, what is V here my dear? V.

[00:28:06]Okay. So C is equal to Q² by W Q² and A² T² W and M L².

[00:28:16]Okay. So it's very simple that mass comes to become M^us 1. L will L square will become L^ minus2. T power minus 2 comes to numerator become T square. T square T square is going going to become T^ 4 and A². This is going to be the dimensional formula for capacitors. So no dimensional formula you have to buy hotter everything is created.

[00:28:38]Okay now just see huh so what is the dimensional formula toughest dimensional formulas but you should know that he'll give mass the following sometimes in dimensional formulas or he will ask you to find out what is the dimensional formula of this or he will ask you to find out the relations write force in terms of mass velocity and acceleration like these type of questions will come.

[00:29:00]So what is the dimensional formula for resistance? So resistance dimensional formula if you want to find out see these are the these are the techniques to remember the dimensional formulas and E is equal to I R R is equal to V by I and electric potential is nothing but work done on unit charge isn't it work done on unit charge just I told you this is ML² T power minus2 charge is nothing but A into T okay that's it so what is the dimensional formula for potential now ml² t power minus 3 a power minus1 so therefore r is equal to m l² t powerus 3 a power minus1 current is also again a okay so r is equal to m l² power - 3 a power -2 to this is the dimensional formula for resistance. Now what is the dimensional formula for inductance? Okay, so what is the dimensional formula for inductance only dimensional formulas? Okay, so what is the dimensional formula for inductance?

[00:30:11]Okay.

[00:30:15]So inductance energy stored is nothing but half LI square. H what is the formula? Energy stored is nothing but half L I² just see.

[00:30:27]Okay. So therefore energy stored energy stored is nothing but half L I².

[00:30:35]This is the formula. You know what is L?

[00:30:37]L is called as inductance.

[00:30:39]You all know in 10th class that this is a resistor and it is having resistance and resistance is nothing but it is a property of a body to oppose the flow of charges. It is a property of a conductor. Resistance this is a symbol of a conductor.

[00:30:53]And if it is written like this means it is opposing to the flow of charges. You say my body is having high resistance because if I go to Shimla, if I go to Kanyakumari my health is not going to damage because I'm very strong. Immunity is very strong. I've got high resistance in my body. I've got very good antibodies which will support my immune system all these things that mean body resistance is good resistance to the diseases. So resistance to the opposition of flow that is called as resistance. But what is the meaning of inductance? H inductance means what? If you consider any wire and you take the wire which is wound like this.

[00:31:28]Understand? If the current passes through this wire, it will oppose the change in current.

[00:31:36]Understood or not? It will induct 1.

[00:31:51]It opposes the change every day.

[00:32:00]Every day if you study two hours and suddenly your father says why don't you study for one more extra hour you oppose that one that is two hours you'll oppose the changes so consistency will not oppose something extra will come but you will oppose so here also it oppose and that is called as inductance okay so that is called as inductance so here energy of energy energy in the inductor is directly proportional to square of the current h energy in this inductor is directly proportional to square of the current what is current flowing air that is square. Okay. So energy is equal to half I square the inductance. What is the meaning of inductance? Opposition to the change in current not the current there are some students 24 hours they want to play they oppose to study.

[00:32:52]He'll oppose and he is called as resistance.

[00:32:57]one girl is there consistently she's studying for for two hours that is not called as resistance if I ask her to study one extra hour she opposes that is called as inductance understood what I'm saying now so inductance so how do you define how do you derive this formula now for inductance once you know the basic formula it's very simple and easy to derive the formula just see so half does not have any dimensional formula L is equal to energy by I² C energy potential energy a quantity of heat energy Q whatever it may be the formula is ML² E power minus2 okay then what is the dimensional formula for inductance energy formula you write ML square powerus 2 here current is taken as a square so inductance dimension formula so easy powerus a power that's going to be your dimension formula formula Okay. So what is the dimensional formula for magnetic field? Okay. So magnetic field which is called as B.

[00:34:26]But there is only one formula which makes that derivation easy. What is that formula? F is equal to B I L. What is this B? See whenever in a wire the current passes through the wire surrounding that wire there is a magnetic field surrounding that surrounding that wire there's a magic field you might have seen that high high powerful wire it will attract the person it is having force of attraction. So whenever the current passes through the wire there is a magnetic field surrounding that wire and here if you keep some other wire here it starts attracting okay it starts attracting huh and how how it will attract for example the current passing through that wire is the current passing through that wire is I and the length of this wire is L and the magnetic field produced in this wire is B then force is taken as B I L and I want B know so it's very simple now B is equal to F by IIL it's very easy to derive formula only from this formula. So B can be taken as F means ML to the power minus 2 I mean A L means L only length of the conductor that's it very simple to derive. So B is equal to M what's happening here now LL gets cancel now so M L is not present just power minus 2 A power minus1 is going to be the dimensional formula for magnetic induction. So what is going to be the dimensional formula for the next thing that is called as perivity to permitivity. See mu not dimensional formula epsilon not is different from mu not epsilon not is different. So b I I have to find out the dimensional formula for b. So how I'm going to find out the dimensional formula for b. So it is just very simple first thing is f is equal to bil and I want to find out the dimensional formula for mu not. So mu i by 2 r what is this formula actually? H in second year there is one chapter called as moving charges and magnetism. Moving charges and magnetism here if in a circle concept they also should get satisfied first units and dimensions.

[00:36:35]How will you understand this one?

[00:36:38]In this current is passing. Now if you the current is passing through this wire then what is the magnetic induction at the middle point at this point. Okay. So and if the radius of the circle is r just remember one thing complex simple thing you remember is magnetic induction at this point is directly proportional to strength of the current.

[00:37:02]Larger the current passing the greater is the magic induction.

[00:37:11]The next thing is B is inversely proportional to R. The larger is the radius, lesser is the B.

[00:37:20]But when you go closer, distance is less conduction will be strong. So if you join these two, you'll get V is directly proportional to I mean constant mu not. So from this you'll get this formula mu not. So how will you find out mu not it's very simple to find out mu not just see see mu not two dimensions mu not is nothing but v into r by i isn't it so mu not is nothing but b into r by e so just now we got the dimensional formula for b so this also no other choice so what is the formula for that for that is mus - 2 a power - 1 / a okay because this comes to okay so these are the dimensional formulas for the tough physical quantities Okay. So, magnetic dipole. Next dimensional formula is magnetic dipole.

[00:38:33]Okay. So, how will you find out the dimensional formula for magnetic dipole?

[00:38:36]Let us discuss about that.

[00:38:39]Okay. So, magnetic dipole is nothing but I into A. What is this formula actually?

[00:38:45]How do you get this I into A? Now, just see here if you consider any atom positive charge is there and surrounding that you know electron is revolving.

[00:38:53]Electron is revolving around the positive charge. So because electron is revolving around the positive charge you know moving electrons creates current.

[00:39:00]Okay. So the current produced by the moving electron is I and the area of this atom. Okay. So what is the area of this atom is taken as a. So magnetic moment because of this atom is nothing but I into A.

[00:39:15]Why is it so? Because if the current if the electron is moving in an anticlockwise direction anticlockwise direction the front part is going to become north pole because for n if I draw arrow it will be anticlockwise the first partic this is the front part which is anticlockwise direction but for back partic clockwise clockwise anticlockwise anticlockwise means northwise so this is going to be north pole and this is going to be south pole so this so this is north pole and this that's why it is called as magnetic dipole Dipole means two poles are there south and north. So now this atom is acting like a magnetic dipole and the current passing is I and the area is going to be a. So what is that? What is the formula for this? See here I mean current A. But this A is nothing but area which is nothing but L square. The dimensional formula is L square area L square. So A into L² I A and L square. So what is the dimensional formula for magnetic intensity?

[00:40:44]Okay. So next what is the dimensional formula? Magnetic dipole planks constant. So what is the dimensional formula for planks constant?

[00:40:57]Okay. See planks conant.

[00:41:09]So what is that actually? There is a sun. From a sun light comes in the form of packets. Light comes in the form of packets. In every packet there is certain energy. And in every packet there is a wave. In every packet there is a wave. That's why light is having both particle and wave nature. Particle wave. That's why it is called as nature.

[00:41:36]Okay. Light is having nature. explained by Max plank. The light is coming from the sun in the form of photon. Each and every packet of energy is called as a photon. And this photon is having certain energy. What is the energy produced by this photon? How much is the energy? Energy is nothing but h into new. New means frequency. New means what? Frequency. Frequency and dela 1 by time period. Okay. So what I'm going to write now E is equal to H by T.

[00:42:08]Energy produced from the sun each and every packet is having an energy of H by T. Now frequency and it's reciprocal of time period. So how do you find out H?

[00:42:18]Now H is nothing but E into T A to energy. I told you energy is written as ML² minus 2 into T. This implies that H is equal to M L² T power minus1. This is the very important dimensional formula for PL's constant. Okay. Next, some more constants we'll discuss which are regularly asked in your examinations.

[00:42:41]What is that? Viscous forces law coefficient of viscosity. H coefficient of viscosity.

[00:42:48]What is the dimensional formula for coefficient of viscosity?

[00:42:53]Okay. Then coefficient of viscosity detail so that it will be easy for you in learning the fluids chapter. fluids first load of viscosity detail but concept so you'll understand isn't it so what is that you know see fluids okay see fluids for example this is a canal fluids flows in the form of layers fluid flows in the form of layers see have you seen have you seen the shape of a canal can you tell me what is the shape of a canal either it is a or b okay canal No, it's having a science behind that.

[00:43:44]It's having a physics behind that. Okay.

[00:43:46]What is the physics behind that?

[00:43:47]So if you construct V shape like this upper layer is having larger area and below layer is having lesser area and below layer is in still lesser area.

[00:43:59]Okay. And uh you know when liquid is flowing in the form of layers upper layer when it is moving forward lower layer will it stop like friction it is having viscous forces in the opposite direction. What is having? It is having viscous forces in the opposite direction.

[00:44:27]This is called as viscous drag. Okay. It is called as viscous drag. This is a viscous forces which will try to stop the upper layer don't go but upper layer will say come along with me.

[00:44:38]That is called as viscous drag.

[00:44:41]That is called as viscous forces. It is acting in opposite direction. it is acting in opposite direction. So these viscous forces are present. So because viscous forces are there and I told you that I have to tell you that viscous forces are directly proportional to area of a below layer. If area of a below layer is lesser than area of above layer, viscous forces also will be less.

[00:45:16]When viscous forces are less, floating will be fast. So flow of speed increase. Understand? So that is called as viscous forces. And one more thing is upper layer is having a velocity of 2 m/s. Lower layer is having a velocity of 1 m/s. And what is this gap? This gap is called as displacement. Okay. Depth. Understood?

[00:45:40]Now viscous forces are directly proportional to velocity gradient. This is called as this is called this term is called as velocity gradient. What is the meaning of velocity gradient? Change in velocity with respect to depth. As you go deeper, velocity decreases. That is called as change in velocity with respect to depth. And it is given as negative. Why?

[00:46:01]That's why it is negative. So what is that? Viscus forces are directly proportional to minus delta v by delta x. So here from all these what are you going to understand? No from all these you will understand one thing. What is that? You'll understand that FV is directly proportional to A minus delta V by delta X. Velocity gradient angles decrease in velocity with respect to depth decrease in velocity is given by delta V depth is given as delta X distance or hope you're understanding.

[00:46:29]So if you if I want to remove this proportionality I'll get a constant which is called as coefficient of viscosity delta V by delta X.

[00:46:37]Okay. So delta this is going to be your formula. From this formula I have to get the formula for coefficient of viscosity. Tell us some formula. Let us see how do you get the formula for coefficient of viscosity. Now see here see of viscosity mean for in the area again velocity in the displacement time. Why do you write delta v? No not necessary just v by x and then h. So f you keep like that only a comes denominator. Delta Vation X goes to numerator. So NA is equal to force is nothing but mass into acceleration and displacement is nothing but L. Area is nothing but L². Velocity is nothing but L^ minus 1, isn't it? Then what is quotient of viscosity? M L cancel. Okay.

[00:47:20]L² cancel then is it okay? So and here L L square cancel here L here L cancel. So only one L is left here. No L power minus one. So here t power minus 1 comes to numerator becomes t power + 1. So -2 + 1 is again minus 1. So what is the dimensional formula for viscosity? Mus power minus one is going to be the dimensional formula for quot of viscosity. Need not by heart of viscosity for i logic for that.

[00:48:07]I'll give one example.

[00:48:13]I'll give one small funny example.

[00:48:28]I'm first. Second for 21.

[00:49:14]21st April. 31st.

[00:49:19]30 second practice.

[00:49:34]This is just to understand because you can't remember understand.

[00:49:47]So best method is to this one. Okay. So the next dimensional formula is what is that gravitational constant?

[00:49:59]Gravitational constant which is represented with letter G.

[00:50:04]gravity chart law so that when I'm discussing gravity it will become very easy okay so what is that formula here for example in the universe Newton says that in the universe every body attracts some other body every body attracts some other body so this body is having mass m1 this body having mass m2 gap between them is r so force is directly proportional to product of the mass force is inversely proportional to square of them Okay.

[00:50:35]Okay.

[00:50:41]Force because masses are lesser.

[00:50:46]Every body in the universe attracts some other body.

[00:51:03]Okay.

[00:51:27]So what is here now? Force is direct.

[00:51:34]So if you remove this what you get now F is equal to proportionality this is a G m1 M2 by R². This is going to be your general formula for gravitation. General you have to bring that one. So gal square F means what? M Lus means radius L² M means M only M² getting cancelus LQ PUS is it okay? Okay so these are very important dimension for us.

[00:52:08]What is the time now?

[00:52:11]My time is over.

[00:52:13]So this is the basics of your dimensional formula. Tomorrow we will start the problems but please come at 8:00 because I have waited for 25 minutes for you. 25 minutes at least 10 problems understood at least 10 problems because see I'm very much tense because you know wonderful thing yesterday I learned I have listened to the interview of brakes you know he's a director of Aiming 75 75 days.

[00:52:59]Exam cancel.

[00:53:23]month.

[00:53:28]So he told that nearly 75 days will be given this time also not one month he's an expert famous student and we can expect minimum two months 40 days I have to complete all the chapters but I can challenge that even in practice 30 Okay. So it's very easy. Don't lose your heart. Those who are getting 300 300 it's very easy. If you got 30 you can get 100. If I get 40 days in pro that you'll get 100 easily easily without any hard work and you will feel that it will be easier than biology and chemistry also.

[00:54:48]Is it not easy? Dimensional formulas.

[00:54:54]Did you get anyenefit today?

[00:55:01]You learned something new. That's it.

[00:55:08]Okay. So give me the complete time from 8 to 8 8 to 8:30 if you give evening 6:00 to 8:30 I will sit with you now problem every day if you complete minimum 50 to 100 problems then only you can crack need 50.

[00:55:30]Okay. So, all the best. Don't lose your Thank you very much.