Electromagnetic Damping

Damping plays an important role in regulating the movement of the material. It is an opposition to the motion of an object. The damping tends to reduce the velocity of a moving object. The object can have various forms of motion; rotational motion, linear motion, oscillatory motion, etc. The number of damping techniques is also used in rotating, moving, and oscillating systems. This involves fluid friction damping, air friction damping, traditional friction damping, and electromagnetic damping, to name a few.

Damping, in physics, inhibits vibratory motion, such as mechanical oscillations, noise, and alternating electrical currents, by the dissipation of energy. If a child does not keep spinning a wheel, his motion dies because of damping. Shock absorbers in vehicles and carpet pads are examples of damping devices.

Electromagnetic Damping Definition - An Introduction

Of all these methods, electromagnetic damping is one of the most interesting damping methods. This uses an electromagnetic current to control/regulate/slow the motion of the body without any direct physical contact with the moving object. To understand this fascinating damping technique, it is important to understand two concepts - Eddy Current and Electromagnetic Induction.

Electromagnetic Damping is associated with eddy currents. 

Electromagnetic Damping Examples

Let us brief you an example to understand the eddy currents - 

Let there be a source of    B vector  B→   Now, if we shift a metallic plate towards and away from the source of B vector  B→  emf will be caused by the Law of Faraday in the conductive plate due to a change in magnetic flux

є= − dФ / dt

є= −dФ dt

Now, what is Electromagnetic Damping - Thermal energy is produced in the plate due to the eddy current in the metal plates. This energy here comes at the cost of the kinetic energy of the moving plate, and therefore the metal plate slows down. This is the fundamental concept behind electromagnetic damping.

To reduce, we need to reduce the flow path of this current. We cut holes in the plate to popularise the available routes. This helps to reduce the number of circular loops through which the current will flow. The loss of energy due to eddy current is therefore reduced and electromagnetic damping is therefore reduced.

Electromagnetic Induction

The concept of electromagnetic induction was first studied by Michel Faraday in 1831. Electromagnetic induction is defined as "Changing magnetic field and inducing emf (electromotive force) into the conductor." Electromagnetic induction is achieved either by moving the conductor through a steady magnetic field or by placing the conductor in a variable magnetic field.

Eddy Current

This induced emf to induce a current across the conductor. This induced current is called the Eddy current. Due to Eddy’s current, the electrons in the conductor follow a unique pattern, swirling around the conductor line, similar to swirling water in the whirlpool.

The eddy current in the conductor is swirling in such a way as to generate a magnetic field in the system. An external magnetic field is also experienced by the conductor. The magnetic field created by the eddy current is opposed to a change in the magnetic field felt by the conductor under Lenz's law. Thus, Eddy's current is flowing perpendicular to the magnetic field.

The Theory Behind Electromagnetic Damping

A damping force is generated when these Eddy currents and magnetic fields interact with each other. It's called electromagnetic damping. Which, by nature, is a resistive force. This is contrary to the motion of the conductor/object. Thus, we may describe that "It is a damping technique where the electromagnetic current slows down the motion of an object without any actual touch".

The Dependency of Electromagnetic Damping

As the distance between the magnet and the conductor decreases, the damping force increases. The electromagnetic damping force is proportional to the induced eddy current, the magnetic field strength, and the speed of the object. This means that the faster the object moves, the greater the damping and the slower the motion of the lower object will be damping, which will result in a smooth stopping of the object.

Electromagnetic Damping

Apparatus:

An aluminium block, a magnet, a magnet holder to hold the magnet.

Procedure:

Hang the magnet out of the aid. Don't put the aluminium plate right now. Take the magnet to one side and release it. It's oscillating like a pendulum. Watch for around 10 oscillations. See if there is a large amplitude damping. Stop the magnet, please. Place the aluminium plate under the hanging magnet. The magnet should not touch the plate, and the partition should be small, say 1~mm. Now pull the magnet to one side and release it. Take a look at the oscillations. Can you watch for ten oscillations? The oscillations are damped very quickly.

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Discussion

As the magnet moves over the plate, the magnetic field changes in time over the parts of the plate. This changing magnetic field generates induced currents on the surface of the plate. These currents are opposed to the cause of the relative motion between the plate and the magnet. As a result, the magnet slows down very rapidly and almost stops at 2 or 3 oscillations.

More About Electromagnetic Damping

Students must have understood about Electromagnetic Damping through its detailed introduction and examples. 

After studying about the theory attached to it and the procedure, students must have been able to strengthen their knowledge about the related concepts. 

Sometimes, during the exam days, students often find it difficult to manage their time and figure out the technique that should be followed. 

But, there’s no one solution to it, everyone must have different habits and so, you can expect yourself to follow a schedule that your friend is following. 

Read ahead to unlock some of the tips that you shall be following despite your personal interests and habits. 

• Identify and write down realistic goals: Realistic goals are the goals that are achievable if given a correct time frame, a good mindset, skills and abilities attached to it. These goals help you to not only get what you want but also what you can achieve. One should set these goals or targets very simple, which can be achieved without fail with little effort. It not only motivates oneself but also encourages to set new targets. The most important aspect that one should keep in their mind while setting the goals is better understanding of oneself, of one's capabilities and one's study pattern and then, nothing is unachievable.

• Assign a reward: Appreciation is the key to motivation. Rewarding yourself for the hard work that you had to put in accomplishing the set goal is very much necessary as it pushes you to achieve it faster and come out with flying colours. Rewards always boost your mood and give you inner happiness. As a result, you set new goals for yourself and try to achieve them faster and with complete accuracy. It also creates a sense of self-belief.

• Visualise: As assigning a reward to self for the hard work is necessary, in the same way, visualising yourself at a better place after achieving the set target or your goal keeps you going. Visualisation increases confidence and the thought that this can happen and will definitely happen without fail, acts as icing on the cake. In order to get success, you have to imagine it or else, it is not going to happen. To get closer to your goals, you have to dream of it, picture yourself as a winner and see the results amaze you, thereafter.

• Get rid of excuses: Excuses are the biggest hindrance in the path of success. Whoever starts making or finding excuses in their tasks, starts moving away from their goals. Excuses always create negative thoughts in ourselves. It reduces our productivity. Instead of finding excuses for not being able to achieve the target ,one should observe their daily work routine, set small targets and plan the day accordingly. So that you can achieve the goal and get your confidence back.

• Work on your 'HOW': After taking the first step of identifying or setting your goals, the very next step is to make a plan to achieve it. Whatever the target is, you have to divide it into simpler parts and start working on it. Following the plan helps you to stay on track and this would always yield results. Students shall note that the ‘HOW’ behind every target is the only process that would help you reach the desired destination. 

To conclude, you might feel like quitting especially in the times of too much pressure and stress but in those times, make sure to remind yourself that these discomforts will help you grow and that’s what you’re working for. Hence, students shall always make it a point to try to overcome all the challenges and push your limits continuously so that they can get closer to their dreams.