Every matter in the universe is composed of tiny particles called molecules. They attract each other with some attractive force. There exists an intermolecular force of attraction between molecules. Every object in the universe cannot move without external force. If force is applied to the object. It will be stored inside and then released in the form of work.
Energy consideration gives the relation between the force applied and the energy needed for applying the force. Lenz’s law is stable with the law of conservation of momentum. While discussing the energy consideration two factors are important such as Lenz’s law and the law of conservation of energy. It takes the concept of motion of emf which is related to the law of conservation of energy.
The capacity of the physical system that needs to do work is called the energy of the system and it is a scalar quantity. It occurs in many forms. The S.I unit for energy is Joule.
Energy is used to power the devices that we are using such as heat, light, etc. The different types of energy sources are used mainly for the production of electricity. Energy is a fundamental quantity that is very important for life. Energy conversion is the process of conversion of one form of energy into another form of energy. All forms of energy-related to motion.
By the conservation of energy law, one form of energy can be transformed into another form and the energy cannot be destroyed or formed. In other ways, it can also be stated that if the system is isolated then the total energy of the system does not change and it remains constant.
When a conductor carrying current is placed in a magnetic field, the changes are produced in the magnetic flux. Due to this change in magnetic flux, there is an emf induced in the circuit. The direction of the induced emf is given by Lenz's motion. By this, the induced emf is given by,
$$\mathrm{E=-N\frac{d \phi}{dt}}$$
Let us consider the coil connected with the galvanometer. Let the north pole of the magnet be moved towards the coil. If the magnet remains constant in its position, then there is no deflection in the galvanometer.
If the north pole of the magnet moves towards the coil there shows a deflection on one side. If it is moved away from the coil then the deflection will be in the opposite direction.
If the magnet moves towards or away from the coil fast then there occurs a large deflection. This happens due to the induced emf in the coil. If the north pole moves towards the coil the induced emf is in the opposite direction which makes the nearer side of the coil to the magnet behave as a north pole.
So there occurs a deflection. If the north pole moves away from the coil then the nearer side of the coil to the magnet behaves like a south pole. And there is no deflection.
Similarly for the south pole if it comes closer to the coil the nearer side of the coil behaves as the south pole and deflection occur. If it moves away from the coil the nearer side behaves like a north pole.
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Keministi, Lenz law demonstration, CC0 1.0
Here the energy consideration is going to be discussed in a quantitatively manner. While discussing the consideration which gives the relation between energy and force, two concepts should be taken into consideration. They are Lenz’s law and the law of conservation of energy. Let us consider a rectangular conductor whose sides are PQ, QR, RS, and SQ. Among these, three sides QR, RS, and SQ are fixed and the side PQ is allowed to move freely. Let us take the resistance of the movable conductor to be r. So the resistance associated with the other three sides is negligible compared to the resistance r. If we apply a voltage across the conductor the current through them is given by,
$$\mathrm{I=\frac{emf}{voltage}=\frac{\varepsilon}{\nu}}$$
$$\mathrm{I=\frac{Blv}{r}}$$
If the coil is placed in the magnetic then there is a current which applies a force on the conductor. The force acting upon the coil is opposite to the direction of the motion of the conductor coil. The force acted on the coil is given by,
$$\mathrm{F=IlB}$$
$$\mathrm{F=\frac{Blv}{r}\times lB}$$
$$\mathrm{F=\frac{B^{2} l^{2} \nu}{r}}$$
Here B denotes the magnetic field strength of the system
l denotes the length of the moving arm
$\mathrm{\nu}$ denotes the velocity of the moving arm in the magnetic field
r resistance of the arm
Due to the induced emf, the moving arm is pushed with velocity v. The power needed for the movement of the conductor is
$$\mathrm{power=force \times velocity}$$
$$\mathrm{F=\frac{B^{2} l^{2} \nu}{r}\times \nu}$$
$$\mathrm{P=\frac{B^{2} l^{2} \nu^{2}}{r}}$$
This energy is dissipated as heat.
$$\mathrm{P=I^{2} r}$$
$$\mathrm{I^{2} r=\frac{B^{2} l^{2} \nu^{2}}{r}}$$
According to Faraday's law of electromagnetic induction
$$\mathrm{\varepsilon=\frac{d \phi}{dt}}$$
Already we know that $$\mathrm{\varepsilon=Ir}$$
$$\mathrm{I=\frac{dQ}{dt}}$$
$$\mathrm{\varepsilon=\frac{dQ}{dt} r}$$
Thus $$\mathrm{\frac{d \phi}{dt}=\frac{dQ}{dt} r}$$
$$\mathrm{dQ=\frac{d \phi}{r}}$$
In this tutorial, the facts about energy consideration and the law of conservation of energy are discussed in detail. Lenz's law and the energy consideration as a quantitative study are also discussed.
Q1. What is energy conversion?
Ans: Energy is a fundamental quantity that is very important for life. Energy conversion is the process of conversion of one form of energy into another form of energy. All forms of energy-related to motion.
Q2. What are the energy sources?
Ans: Energy sources can be divided into two categories such as renewable and non-renewable sources. Renewable sources of energy are the energy that is obtained from flow sources such as wind, tide, sunlight, etc. The energy that is obtained from natural resources which cannot be replaced is called non-renewable sources of energy. Fossil fuels and nuclear energy are some examples of non-renewable sources.
Q3. Give some examples for the conservation of energy.
Ans: In the explosion of dynamics, the chemical energy stored in it is converted into kinetic, heat, and light energy. The total energy calculated by adding the kinetic energy, heat energy, and light energy is equal to the initial chemical energy. Similarly in a loudspeaker, the electrical energy is converted to sound energy.
Q4. What are the consequences of the conservation of energy?
Ans: The first main consequence is that the perpetual motion of the system cannot exist. That is, it is not possible for a machine to continuously deliver energy without any disturbance. All systems do not have translation symmetry. So the conservation of energy is not possible for all systems.
Q5. What are the applications of Lenz’s law?
Ans: Lenz’s law has many uses. Among these, some of them were given below. It was useful in the braking system of trains, metal detectors, AC generators, microphones, balancing eddy current, and card readers.
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