Podsumowanie wiadomości z elektrostatyki

Prepare answers for repetition questions from electrostaticselectrostaticselectrostatics.

1. Describe in brief the properties of the electric charge.

In nature, there are two types of electric charges: positive and negative. Charges with the same signs (like charges) repel each other, while charges of different signs (unlike charges) attract. The instrument used to study how much bodies are charged is an electroscope.

2. What does it mean that a body is charged?

The charged body has an excess of charge of one sign.

3. List methods of chargingchargingcharging bodies.

There are three basic methods of charging bodies: by friction, by contact and by induction (influence).

4. Discuss chargingchargingcharging bodies by friction.

Charging by friction involves the flow of charges (electrons) from one body to another. One of the rubbed bodies is charged negatively and the other positively.

5. Discuss chargingchargingcharging bodies by contact.

Charging by contact involves touching an electrically neutral body with a charged body. As a result, the neutral body is charged with the same sign as the body it got in contact with.

6. Discuss chargingchargingcharging bodies by induction.

Charging by induction involves bringing a charged body close to an electrically neutral body, whereby the charge will be displaced in the neutral body.

7. Formulate the law of electric charge conservation.

The law of charge conservation says that in an isolated system of bodies, the total electric charge (the sum of positive and negative charges) does not change.

8. What do all bodies consist of?

All bodies are made up of very small atoms. The atom's radius is of the order of 10Indeks górny -10^-10 m. Each atom consists of a positive nucleus, around which the negative electrons move at very high speed.

9. What are the parts of the atomic nucleus?

The atomic nucleus consists of protons that have a positive charge and neutrons that are electrically neutral. The mass of neutron and proton is very similar (neutron is slightly heavier). The electron mass is 1836 times smaller.

10. What is the elementary charge and what is its value in the SI system?

The unit of electric charge is 1 C (coulomb). The electron and proton charge has the same value, called the elementary charge. This charge is equal to: e = 1.6 $·$ 10Indeks górny -19^-19 C. Each charge is a multiple of the elementary charge.

11. What is an ionionion and how it is formed?

Electrons orbit around the nucleus at different distances, on so‑called electron shells. The last shell is called the valence shell. The electron (or several electrons) can be detached from the shell, and a positive ion is formed. When additional electrons get on the valence shell, a negative ion is created - the anion.

12. Introduce Coulomb's law.

Each two electric charges act on themselves with electrostatic force. Coulomb's law says that the magnitude of this force is directly proportional to the product of the magnitudes of these charges, and inversely proportional to the square of the distance between them. The force acting between the charges is calculated from the formula:

where k is a certain proportionality factor, which is equal to $9\cdot {10}^9\frac{N\cdot m^2}{C^2}$ in vacuum.

13. Show how substances can be divided due to electrical properties.

The bodies differ from each other in electrical properties. Depending on whether there is a possibility of free flow of electric charges, we divide the substances into insulators and conductors.

14. How are insulators built?

Insulators are materials whose internal structure is characterized by the fact that electrons are very strongly bound to atoms. They cannot easily break away from atoms and do not have the possibility of free movement within the body. They can be charged by friction - then some electrons detach themselves from atoms and go to the surface of the other body. Insulators include among others glass, porcelain, plastic, wood, rubber, distilled water, air.

15. How are conductors built?

Conductors are bodies in which electric charges can move freely. The conductors are, for example, metals. Valence electrons in metal atoms are not bound to atoms and can move within the entire body of metal. They form so‑called electron gas. The conductor can be charged if it is isolated from the ground.

Summary

• In this section, we presented information about electric charges, their origin, types and laws governing the interactions between them. We showed how you can find out about the existence of charges and see what determines the strength of their interaction. We gave the classification of materials due to electrical properties and presented examples of insulators and electric conductors.

Exercises

Glossary

Keywords

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electrostaticselectrostaticselectrostatics

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