Metodi di elettrizzazione a confronto

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1 Metodi di elettrizzazione a confronto

2 La polarizzazione

3 electric charge 1)Fill in each gap the correct word from the list: attracts, amber, transfer, small, rubbed, charged, net, dust, excess, polarisation, static, wool. The ruler is …………. by being ……… with a cloth towel. Electrons ……….. from the cloth to the ruler, leaving it with a …… negative charge. The ………….. electric charge on the ruler induces a …………… (separation of charge) in scraps of paper, and thus …………… them. This phenomenon is called ……….. electricity. The ancient Greeks knew that a piece of …………. would attract …………. pieces of leaves or ………… after being rubbed with some ………….

4 electric charge and its conservation
Are all electric charges the same, or is there more than one type? 2) Choose the correct word: Charge comes in a lot of/two types, positive and negative; like/unlike charges repel and equal/opposite charges attract. The law of conservation/equilibrium of electric/magnetic charge: whenever a certain amount of charge is produced on one object, an equal amount of charge of opposite sign is produced on another. Electric charge can neither/either be created nor/or destroyed.

5 insulators and conductors From an atomic point of view:
3)Fill in each gap the correct word from the list: insulators, conductor, tightly, most other materials, good conductors, loosely, metals, insulator. Conductors Charge flows freely: …………….. Insulators Almost no charge flows: ………………… From an atomic point of view: • for ………………………, the electrons are bound very ………… to the nuclei; • for ………………………, some of the electrons are bound very ………….. and can move freely within the material. The relative magnitude of conductivity between silver (a good ………………….) and rubber (a good ………………….) is on the order of 1021.

6 Charging by conduction/induction Charging by conduction/induction
charging methods 4) Choose the correct word to describe the pictures below: Charging by conduction/induction If a positively/negatively charged metal rod is brought close/into contact contact with a charged/an uncharged metal rod, the free electrons/protons in the neutral rod are attracted by the positively charged rod and some will/won’t pass over to it. Charging by conduction/induction If a positively/negatively charged rod is brought close/into contact to an uncharged metal/insulator rod, but does not touch it, the free protons/electrons in the neutral rod do not leave it but move within the metal rod towards/far from the external positive charge.

7 electroscope 5) Complete the text:
An electroscope is a ………………….. used for detecting charge. It is made of two metal ……………. that are free to move (often made of gold), which are situated …………………… an isolated case. The electroscope on the left is charged by ……………… and the one on the right by …………………….. A previously charged electroscope can be used to determine the ………… of a charged object.

8 Charge on the electron:
atoms and molecules 6) Complete the text: Only within the past century has it become clear ………. an understanding of electricity originates …………. within the atom itself. This simplified model ……. an atom shows a small, dense, positively charged nucleus containing a mixture of protons …… neutrons surrounded … negatively charged electrons. All protons and electrons have exactly the ……… magnitude of electric charge. Charge on the electron: In the ……., the unit of electric charge is the Coulomb. Electric charge is …………. in units of electron charge. The ………… charge carried by any object is a whole …………. of the electron charge. A polar molecule is ……………. overall, but its charge is not ………….. distributed. water molecule e = −1.602× 10−19 C

9 learning the basics 7) Decide if the following statements are true or false: T F In a good conductor, the electrons are bound very tightly to the nuclei. When an electroscope is charged, the two leaves repel each other and remain at an angle. Like charges attract. A positively charged object has lost electrons. Charging by conduction works without ever touching the object to be charged to the object used to charge it. Electric charge permits to charge two objects with opposite charge on them.  j j j j

10 either with dry hair or with wet hair
An extra experiment 8) Do it at home. Explain in Italian and in max 10 lines what do you observe. MATERIALS 1 comb Some pieces of paper Try to charge the comb either with dry hair or with wet hair What does happen?