Hello students, today we are going to study three important laws of chapter number one which is introduction, which are very important from the exam point of view, which will be zero law, first law and second law, so I hope you are ready with your paper, so without wasting time let's start this video. So first of all let's understand the zero law. Now, in the zero slope field, we will have to consider three bodies A, B and C, that is, we have taken three such bodies whose names are A and C, so zero law tells that if body B is in thermal equilibrium with body A, then what is the fact that body B is in thermal equilibrium with body A, what does this arrow tell that both B and A are in thermal equilibrium with each other, you are in thermal equilibrium, thermal equilibrium means the temperature of body A is the same as the temperature of body B, for example, if the temperature of body A is 80 degrees, then what will be the temperature of body B. 80 degrees only then we will say that both A and B are in thermal equilibrium with each other, okay then zero, so this tells that and if body C is also in thermal equilibrium with A, body C is also in thermal equilibrium with A, that is, the temperature of both A and C should be the same, that is, the temperature of A should also be 80, that is, 80 degrees centigrade, only then both A and C are in thermal equilibrium, that is, the temperature of both, so what does this lock tell that if the temperature of B is equal to A, that is, body B is in thermal equilibrium with A, body C is in thermal equilibrium with A, then we can say that these two bodies B and C will also be of the same temperature, that is, both the bodies will also be in thermal equilibrium with each other, so it is a simple statement, let us see that one body B and C, that bodies B and C are in thermal equilibrium with body A means B is the equilibrium with A, C is the thermal equilibrium with A, then what can we say, let body B and C, let body B and C are also in thermal equilibrium with each other, so what will happen with each other, they will be in thermal equilibrium, so I hope you have understood this law, next is Fox's law, now we have already studied the first law in 12th, in 10th also, which we call the law of conservation of energy, what we saw in it, we saw that we cannot create energy and we cannot destroy it also, but we can change energy from one form to another, we can convert it, so the same law is written here that energy net B, we cannot create the created energy, we cannot destroy it also, but it can change its form from inside, we can change its form, like work energy, if this is our system, if I work it in my hands, if I work it, then by doing this, Ghisu square two and keep it here, then what We will get heat, that is, work has been converted into heat and if we talk about the engine, then what happens in the engine, we put fuel, combustion of fuel takes place, heat is produced, what happens due to heat, the shaft of the engine starts rotating due to which we get work, so here is our first law, take a screenshot, next let's see, the next law is the second law, now this second law was made by two scientists, first the scientist was the Kelvin Planck, he had given a statement, second the scientist was the Kelvin Planck, he had given a statement, if we combine the statements of both, then it becomes the second law, first let's see the statement of the Kelvin Planck, so what Kelvin Planck did was that he took a heat engine, that is, he took an engine, he placed that engine between two reservoirs, the reservoir, that is, the storage of energy is called reservoir wire, he called one reservoir as source, source means a kind of reserve wire from where we will take heat energy and he called the other reservoir Shring shrink means is that also a kind of reservoir where we reject heat energy, we have said the temperature of the source is t1 and they have said the temperature of the horn is t2 and here we assume that t1 is greater than t2, that is the temperature of the source is greater than the horn, okay now we took the heat engine and placed it between the two and what they said is that if this heat engine has to produce work, if the heat engine has to produce work, then the heat engine will have to compulsorily exchange its heat energy q1 and q2 with this reservoir, only then can the heat engine produce work, once again if the heat engine has to produce work then what is the condition, then this heat engine will have to exchange its heat energy q1 and q2 with these reservoirs which are at different temperatures t1 and t2, only then can the heat engine produce work, so the same The statement here says that if an engine wants to produce work, then you need to exchange heat energy between two different temperatures. Here we can see that heat energy is moving from higher temperatures to lower temperatures. We know that heat pumps, that is, a device which can maintain higher and lower temperatures than the surrounding temperature. That heat pump can maintain a temperature higher than the surrounding temperature or even lower than the surrounding temperature. That heat pump is placed in the middle of the source of the ring, placed between two reservoirs. Okay, heat can also move from lower temperatures to higher temperatures. Generally, we know that heat always moves from higher temperatures to lower temperatures, but the closest What I said was that heat can also go from lower temperature to higher temperature, if it has to be taken then it cannot go automatically, so if we have to sell the heat from lower temperature to higher temperature, then we will have to give some work from outside to this heat pump, that is, if work is not given to the heat pump, then the heat will always go from higher to lower temperature, it will go like this, but if we give some work to the heat pump, then what will happen, when will the heat go from lower to higher, only when will it go from lower to higher, only when will the heat flow from lower temperature to higher temperature, so in the same statement it is written that heat can flow from lower temperature to higher temperature, this lower temperature, this higher temperature, how is T2, it can flow from lower to lower only, when, but for that, some external work, what for date, if it has to flow, then but for date, some external work must be applied on it, so in this video that's it That's all, in our next video we will bring what is an open system, what is a closed system, what is an isolated system, what is the surrounding universe, so till then keep reading and wish you the very best.