Description of the Experience
People long ago knew magnets, although they did not know to explain their properties, which were not important at that time. At last even nowadays many people do not know why an iron is heating or why mixer turns around rapidly. And this is not possible or essential for life, it must be a man curious to know the nature of phenomena and also at the level of current technology that peple use it is not even possible. Knowledge is big and each area becomes very specialized.
Each magnet has two poles – north N and South S. At small stick magnets they are usually marked by red and blue colour. If we divided magnet into parts there would always had been two poles, magnetic monopole does not exist. Magnetic field is the only one that students know from their experiences, they know that the same poles are pushed apart and that different poles attract each other.
Magnetic field is represented by induction lines which are continuous and pass through the magnet. It is the only physical field where I can show to students also induction lines, you just have to sprinkle metal scobs at paper and put the stick magnet under the paper. It is very easy but also very demonstrative experiment.
Around every conductor through which passes electric current the magnetic field is created. This is absolutely crucial sentence from which it is clear that electrical and magnetic phenomena are something like two sides of one coin. Later by the end of 19th century the theory of electromagnetic field is created but you have to describe it individually. The theory of electromagnetic field is too difficult for them.
In the vicinity of direct conductor through which passes electric current are induction lines in the shape of circles which have their centre on the conductor. It is needed to determine orientation of induction lines and it is done according to the law of the right hand. Even coin which is actually conductor wound around the core behaves as a magnet when electric current passes through it. In practice electromagnets are used for lifting large metal loads, for example the metal scrap yards. The only problem is that when the power goes out the electromagnet loses its magnetic properties and the load falls.
Amperes law – it describes behaviour of two direct parallel conductors through which passes electric current. In the case that current passes in both conductors in the same way the conductors attract each other otherwise they repel each other. It is the expression of the action of magnetic field of both conductors. Since there is a motion there has to be force applied and that is defined by Amperes law.
F=k.i.i.l/d
From technical reasons I had to change the sign of currents to small I and their length is l and the distance between them is d. On the basis of this law is defined the unit of electrical current, 1A. The definition is too difficult for students. From the law it results that the force applied is increasing with current which is passing through conductors, their length and decreases with the distance between conductors.
Magnetic field itself is described by some units, for example magnetic induction, intensity of magnetic field H …
It is difficult to say whether the students will understand the topic. They have already know basic terms from their primary schools.
From history it is needed to mention a compass which had fundamental impact on sea cruise because until then the sailors oriented only thanks to the stars or the Sun. Also our planet is one big magnet the field of which is constantly changing.
I consider this experience as positive.
In order to post a comment it is compulsory to be logged in.
