What I knew?
Electromagnetism, upon hearing this word the first thing that came into my mind was magnet; it has the South and the North magnetic Pole. And also i remember our subject Electronics during our grade 10 days. We somehow touched some topics about electromagnetism.
What I learned?
In this lesson i know somehow i already have a clue on what the topic is all about because i got a slight background about this topic.
Let’s start discussing about the topics I learned in this lesson…..
On Electromagnetism this is the forces and fields with charge. It is also defined as the production of magnetic field by current flowing in conductor. There are two aspects of electromagnetism which is the electricity and magnetism, as when an electric current or a changing electric field generates a magnetic field, or when a changing magnetic field generates an electric field.
This arrangement is called a solenoid. The more turns we wrap on this core, the stronger the electromagnet and the stronger the magnetic lines of force become.
Electromagnets have become as a vital component in most of the electronic devices such as loudspeakers, motors, generators, magnetic separation equipment, hard disks, scientific equipment and much more. Its ability to turn magnetism on and off instantly is one of the important features responsible for its growing usage in modern electronic devices.
Even most of the home applications such as door bells, circuit breakers and music amplifiers in guitar use electromagnets to perform a wide range of functions. For example, when the button in the door is pushed electricity starts to flow over the electromagnet making it magnetic and clanging metal bell and metal clamp together causing a ringing sound. Once the button is released electricity flow shuts down thus, stopping the ringing sound.
With its amazing features, electromagnets have become as an integral part of modern technologies. Usually, electromagnets are made from coils of wire that carry electricity. When electricity flows through metal coil, electromagnets become magnetic and retain its magnetism until the current stops.
This illustration shows the magnetic field around a current-carrying wire. The current (capital letter “I”) is represented by the white arrow. The magnetic field (capital letter “B”) is represented by the red arrows
The right-hand rule, used to predict the direction of the magnetic field induced (or created) by a current. When you point the thumb on your right hand in the direction of current flow, your fingers curl in the direction of the magnetic field. If the current reverses direction, the magnetic field lines will also reverse direction.
Magnetic flux?
Magnetic flux is a measurement of the total magnetic field which passes through a given area. It is a useful tool for helping describe the effects of the magnetic force on something occupying a given area. The measurement of magnetic flux is tied to the particular area chosen.
The simplest example of induced electric field is the one generated inside a small circular conducting loop due to a changing magnetic field and responsible for the consequent current. Generally speaking, the induced electric field depends, not only on how the magnetic field, , changes with time, but also on how the geometric relation between the loop and magnetic field may change as well. The most basic definition is the magnetic flux through a plane figure due to a uniform magnetic field.
The vector labeled ‘normal’ is our unit vector , and the magnetic flux through the plane area is defined to be
Φ = BA
Faraday’s Law
In this law it states that any change in the magnetic environment of a coil of wire will cause a voltage (emf) to be “induced” in the coil. No matter how the change is produced, the voltage will be generated. The change could be produced by changing the magnetic field strength, moving a magnet toward or away from the coil, moving the coil into or out of the magnetic field, rotating the coil relative to the magnet, etc.
Faraday’s discovery in 1831 of the phenomenon of magnetic induction is one of the great milestones in the quest toward understanding and exploiting nature. Stated simply, Faraday found that a changing magnetic field in a circuit induces an electromotive force in the circuit; and the magnitude of the electromotive force equals the rate at which the flux of the magnetic field through the circuit changes. The flux is a measure of how much field penetrates through the circuit. The electromotive force is measured in volts and is represented by the equation.
Lenz’s Law
Lenz’s law is named after the German scientist H. F. E. Lenz in 1834. Lenz’s law obeys Newton’s third law of motion (i.e to every action there is always an equal and opposite reaction) and the conservation of energy (i.e energy may neither be created nor destroyed and therefore the sum of all the energies in the system is a constant).
Lenz’s law is based on Faraday’s law of induction.When a changing magnetic field is linked with a coil, an emf is induced in it. This change in magnetic field may be caused by changing the magnetic field strength by moving a magnet towards or away from the coil, or moving the coil into or out of the magnetic field as desired. Or in simple words, we can say that the magnitude of the emf induced in the circuit is proportional to the rate of change of flux.
Lenz’s law states that when an emf is generated by a change in magnetic flux according to Faraday’s Law, the polarity of the induced emf is such, that it produces an current that’s magnetic field opposes the change which produces it.
The negative sign used in Faraday’s law of electromagnetic induction, indicates that the induced emf ( ε ) and the change in magnetic flux (δΦB) have opposite signs.
Where,
ε = Induced em
δΦB = change in magnetic flux
N = No of turns in coil
Law of Magnetic Poles
The most basic law of magnetism is that like poles repel one another and unlike poles attract each other; this can easily be seen by attempting to place like poles of two magnets together.
Further magnetic effects also exist. If a bar magnet is cut into two pieces, the pieces become individual magnets with opposite poles. Additionally, hammering, heating or twisting of the magnets can demagnetize them, because such handling breaks down the linear arrangement of the molecules. A final law of magnetism refers to retention; a long bar magnet will retain its magnetism longer than a short bar magnet.
How i learned?
In this lesson there are different laws that was teach by our teacher and in order for us to understand more he let us do an activity were he only gave us the materials and he let us discover and prove the relationship of induced emf and magnetic flux. in other groups they are also tasked to prove the relationship of induced emf and time, induced Emf and number of turn and lastly induced Emf and the negative sign in Lenz’s law.
Electromagnetic Induction
(Faraday’s Law and Lenz’s Law)
OBJECTIVE:
- To prove Faraday’s Law and Lenz’s Law
(Identify the factors affecting the magnitude of induced emf.)
MATERIALS:
- Magnets (3) with varying sizes
- Solenoid
- Galvanometer
- Alligator Wires
- Timer Ballpoint
- Record Sheets
PROCEDURES:
- Gather all the materials.
- Connect the alligator wires to the galvanometer as well as the solenoid.
- Using the connected galvanometer and solenoid, next is to insert one by one on the three different magnets (varying sizes) back and forth within 20 seconds.
- Observe or identify the induced current of each magnet and record it in the record sheets.
RESULTS AND DISCUSSIONS:
Table 1. This shows the actual data and relationship between different sizes of magnets and induced emf.
| Magnets(varying sizes) | Δt(time in seconds) | N(number of turns) | E(induced emf) |
| Long | 20 | 100 | 300 |
| Medium | 20 | 100 | 200 |
| Short | 20 | 100 | 100 |
In this table it shows the relationship between the different sizes of magnets and induced emf (E). the magnet that has the longer in size has the highest induced emf and the shortest magnet has the lowest induced emf. This shows that the longer the size of magnet the greater the induced emf compared to the shorter magnet that has lower emf.
As the magnet moves back and forth, the pointer of the galvanometer moves. If we move the magnet back and forth continuously the pointer of the galvanometer moves also continuously. We also observed that the faster we move the magnet back and forth the higher the emf.
Table 2. This shows the actual data and relationship between magnetic flux and induced emf.
| Magnets(varying sizes) | E(induced emf) | Φ(magnetic flux) |
| Long (Strong) | 300 | 60 |
| Medium (Moderate) | 200 | 40 |
| Short (Weak) | 100 | 20 |
This table shows the relationship between magnetic flux (Φ) and induced emf (E). Time (Δt) and the number of turns of the coils (N) is constant. The strength of the magnets is based only by its size wherein it was assigned that the magnet 1 with the greater induced emf (300) was directly substituted in the formula Φ = which we derived it from the formula E = -N obtaining a value of Φ = 60. The other 2 magnets were also substituted in the said formula; magnet 2 with moderate induced emf came up with 40 magnetic flux and magnet 3 with lesser induced emf came up with 20 magnetic flux.
This proves that the induced emf (E) is directly proportional to the magnetic flux Φ. As the magnetic flux increases, the induced emf also increases and vice versa.
Additionally, magnets vary strengths in terms of materials, size and shape. One way to identify the strength of magnets is on how many objects can attract like for example the thumb tacks.
After gathering all our data this is not yet the end of the task. Our teacher let us visit also the different groups for them to explain and prove also the one that they are assigned to do.
On the relationship of induced Emf and number of turns is directly proportional to each other as the induced emf increases the number of turns also increases.
On the relationship of induced emf and time are inversely proportional to each other, this means that as the induced Emf increases the time decreases and vice versa.
On the negative sign this means that the induced Emf sends current in a direction so as to oppose the change in flux causing it.
Conclusion
Electromagnetism plays a vital role in our everyday life, there are thing that cannot work without it. Just like the generator, doorbells, speakers, computer hard drives, multiple household appliances and etc.These are just some examples of the things we use everyday using electromagnets. Imagine the computer hard drive without electromagnets, how students will be save their files? i just really don’t know.
In addition, this lesson I came to realize that not all things needs a complicated solution and answer. Just kike the task given to us, we overthink and some of the data that we found was not correct.
Finding the different relationship of the induced emf, time, magnetic flux and the negative N somehow a wake up call that not everything is complicated like we think, sometime it’s all about common sense.
Different aspects have different relationship, sometimes it can be directly or inversely. Just life, there are things that directly for us and inversely not for us that help us to grow more and find out what we are really up to.
kisharconado 
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