| Abstract | Iz svakodnevnog života poznato je da se djelovanje između dva nabijena tijela odvija bez vidljivog posrednika (npr. ako se balon trlja po kosi, počet će privlačiti vlasi, na isti način natrljani komad stakla privlačit će vunu itd.), prva takva zapažanja zabilježena su 600 godina prije nove ere. Ono što se tada nije znalo, a danas je poznato, je da se takva djelovanja pripisuju postojanju dvaju električnih naboja koji su nazvani pozitivnim i negativnim. Također je poznato da se istoimeni naboji odbijaju, a raznoimeni privlače. U popunjenom atomu svakog elementa broj pozitivnih i negativnih naboja je jednak, a između njih djeluju električne sile. Tijelo je električki neutralno kada su svi atomi popunjeni elektronima, tada izvan atoma nema električnog djelovanja. Pri određenim uvjetima neki elektroni iz valentne ljuske atoma mogu se odvojiti i smjestiti se u prazni prostor između ostalih atoma. To se odvija i tijekom, već spomenutog, trljanja staklenog štapa vunom, točnije, s površine stakla neki se elektroni istrgnu i ostanu na vuni. Na taj način stakleni štap postaje pozitivno naelektriziran, jer ima višak pozitivnog naboja, a vuna negativno naelektrizirana, jer ima višak otrgnutih elektrona. Višak pozitivnog naboja na štapu miruje kao i višak negativnog naboja na vuni. Tako stvoreni višak naboja zove se statički naboj, a grana fizike koja se bavi proučavanjem pojava između električki nabijenih čestica, elektrostatika. Prva kvantitativna istraživanja između dvaju naelektriziranih tijela proveo je Charles de Coulomb, eksperimentalno na torzijskoj vagi. Te je došao do zaključka, danas poznatog kao Coulombov zakon, koji glasi: „Dva se mirna električna naboja odbijaju ili privlače silom koja je razmjerna umnošku njihovih naboja, a obrnuto je razmjerna kvadratu njihove udaljenosti.“. Obzirom da je izvedba torzijske vage vrlo zahtjevna i teško izvediva u učionicama, što se odnosi i na mnoge druge eksperimente koji su tijekom povijesti provedeni u svrhu otkrivanja raznih fizikalnih zakona, u nastavi se koriste isključivo matematička objašnjenja. Takav način predavanja, ali i učenja je vrlo nezahvalan zbog nemogućnosti vizualizacije često apstraktnih pojmova. U svrhu boljeg razumijevanja, ali i potencijalno veće zainteresiranosti učenika i studenata za gradivo fizike, sve se više uvode aplikacije koje koriste tehnologije poput proširene stvarnosti. Takva je i aplikacija CoulombsLawAR. Vrednovanje njene korisnosti, koje je karakteristično za aplikacije te vrste, provedeno je među studentima prve godine prijediplomskog studija Fakulteta kemijskog inženjerstva i tehnologije u obliku ankete koja se sastojala od četiri dijela (SUS, HARUS, UX upitnici te otvorena pitanja), a dobiveni rezultati pokazuju zadovoljstvo ispitanika. Sveukupan dojam je pozitivan, aplikacija je pomogla studentima u razumijevanju gradiva, no potrebno je ukloniti neke tehničke poteškoće. |
| Abstract (english) | It is known from everyday life that the action between two charged bodies takes place without a visible intermediary (e.g. if a balloon is rubbed on the hair, it will begin to attract hairs, in the same way a rubbed piece of glass will attract wool, etc.), the first such observations were recorded in 600 years BC. What was not known then, and is known today, is that such actions are attributed to the existence of two electric charges, which are called positive and negative. It is also known that charges of the same name repel, and charges of different names attract. In a filled atom of each element, the number of positive and negative charges is equal and electric forces act between them. A body is electrically neutral when all atoms are filled with electrons and then there is no electrical activity outside the atoms. Under certain conditions, some electrons from the valence shell of an atom can be separated and placed in the empty space between other atoms. This also takes place during the already mentioned rubbing of the glass rod with wool, more precisely; some electrons remain on the wool after being torn off the surface of the glass. In this way, the glass rod becomes positively electrified, because it has an excess of positive charge, and the wool becomes negatively electrified, because it has an excess of torn electrons. The excess positive charge on the stick is at rest, as is the excess negative charge on the wool. The excess charge thus created is called static charge, and the branch of physics that deals with the study of phenomena between electrically charged particles is called electrostatics. Charles de Coulomb conducted the first quantitative research between two electrified bodies, experimentally on a torsion balance. He concluded that two stationary electric charges repel or attract each other with a force proportional to the product of their charges, and inversely proportional to the square of their distance – Coulomb’s Law. Given that, the execution of the torsion balance is very demanding and difficult to perform in classrooms, which also applies to many other experiments that have been conducted throughout history for discovering various physical laws, that is the reason why in classes professors are using only mathematical explanations. This way of teaching and learning is very ungrateful due to the impossibility of visualizing often-abstract concepts. For the purpose of better understanding, but also potentially greater interest of pupils and students in physics material, more and more applications that use technologies such as augmented reality, are being introduced. Such is the application of CoulombsLawAR. The evaluation of its usability, which is characteristic for applications of this type, was carried out among first-year undergraduate students of the Faculty of Chemical Engineering and Technology in the form of a survey consisting of four parts (SUS, HARUS, UX questionnaires and open-ended questions). The obtained results show the satisfaction of the respondents. The overall impression is positive, the application helped students in understanding the material, but some technical difficulties need to be removed. |
