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The law of conservation of electric charge

Source: licencja: CC 0.

Zasada zachowania ładunku elektrycznego

You will learn
  • formulate and experimentally confirm the law of conservation of charge in English.

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nagranie abstraktu

Prepare the answers for the introductory questions.

  • What is the electric charge?

  • List the properties of electrical charge.

  • List the three methods of charging bodies.

The law of conservation of electric charge
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nagranie abstraktu

The law of conservation of electric charge is one of the basic laws of nature.

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nagranie abstraktu

It says that in the isolated system, the total electric charge, which is the algebraic sum of all charges of the system of bodies, does not change.

This means that the electric charge cannot be created or destroyed. You can only cause its displacement from one body to another, thereby causing charging of the bodies.

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Pokaz slajdów – zachowanie ładunku elektrycznego. Instrukcja obsługi z poziomu klawiatury: 1. Uruchomienie aplikacji - ENTER, 2. Na każdym ze slajdów czytany jest automatycznie tekst alternatywny po polsku, 3. Przy pierwszym uruchomieniu na pierwszym slajdzie, czytanie tekstu po angielsku - TAB, 4. Przejście między slajdami: do następnego slajdu - TAB, do poprzedniego slajdu - TAB + SHIFT, 5. Przejście do czytania napisu po angielsku - strzałka w górę + strzałka w dół (czyta tekst po angielsku widoczny na slajdzie).
Conservation of electric charge
Source: GroMar, licencja: CC BY 3.0.
Experiment 1
Experiment 1
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nagranie abstraktu

Perform the above experiment. Check the following research hypothesis: the total chargetotal charge total charge of the system is conserved.

Experiment 2
Experiment 2
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nagranie abstraktu

You will need three electroscopes to perform this experiment. Perform an analogous experiment with three electroscopes and also show that the total chargetotal charge total charge of the system is conserved. Repeat the experiment with different electroscopes systems connected by conductors.

Summary
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nagranie abstraktu
  • Electric charges cannot be destroyed nor can be created - they can only move.

  • In electrically isolated systems, the total electric charge (algebraic sum of positive and negative charges) does not change.

The two above statements are independent formulations of the law of charge conservationcharge conservationcharge conservation; each of them underlines a different aspect of this law.

The electrically isolated systemisolated system isolated system is a system in which the charge is not exchanged with the surroundings.

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nagranie abstraktu

The principle of charge conservationcharge conservationcharge conservation allows to explain the course of many phenomena, which include charging bodies (by friction, contact and induction), principles governing the flow of electric current (Kirchhoff's first law) and many phenomena in the micro world, e.g. nuclear reactions.

Exercises

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Exercise 1
Wersja alternatywna ćwiczenia: Determine which sentence is true. Możliwe odpowiedzi: 1. In the isolated system, the charge may move., 2. During charging by friction, the total charge is reduced., 3. In the isolated system, the charge cannot move., 4. During charging by contact, the total charge is reduced.
Exercise 2

If two spheres with different radii are in contact with each other, the charge will not evenly split into both spheres in the process of charging. It turns out that the bigger the radius of the sphere the bigger the charge will be on it. Mathematically, you can write that QR (Q is the charge on the sphere and R radius of sphere). A metal ball with a radius of 2 cm rests on a stand made of an insulator. First, we connect the ball using a thin metal conductor with a second ball with a radius of 1 cm. It turns out that the total chargetotal charge total charge of both balls is then 6 mC. We connect a third electrically neutral ball with a radius of 3 cm using a thin conductor with a first ball with a radius of 1 cm. Calculate what charge will flow through the conductor to the third ball.

Exercise 3

Does the process of charging lead to the production of electrons? Does the excess of charge in one place always correspond to its deficiency in another? Can a negative charge be obtained without producing a positive charge?

Write short answers to the above questions with justification in English.

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Exercise 4
Wersja alternatywna ćwiczenia: Indicate which pairs of expressions or words are translated correctly. Możliwe odpowiedzi: 1. zachowanie ładunku - charge conservation, 2. ładunek sumaryczny - total charge, 3. układ izolowany - isolated system, 4. zasada zachowania - total charge , 5. ładunek sumaryczny - charge conservation
zadanie
Source: GroMar, licencja: CC BY 3.0.
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Interaktywna gra, polegająca na łączeniu wyrazów w pary w ciągu jednej minuty. Czas zaczyna upływać wraz z rozpoczęciem gry. Jeden ruch to odkrywanie najpierw jednej potem drugiej karty z wyrazem. Każdy wyraz jest odczytywany. Kolejny ruch to odkrywanie trzeciej i czwartej karty. W ten sposób odsłuchasz wszystkie wyrazy. Nawigacja z poziomu klawiatury za pomocą strzałek, odsłuchiwanie wyrazów enterem lub spacją. Znajdź wszystkie pary wyrazów.
Source: Zespół autorski Politechniki Łódzkiej, licencja: CC BY 3.0.

Glossary

charge conservation
charge conservation

zachowanie ładunku

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wymowa w języku angielskim: charge conservation
total charge
total charge

ładunek sumaryczny

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wymowa w języku angielskim: total charge
isolated system
isolated system

układ izolowany

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wymowa w języku angielskim: isolated system
conservation law
conservation law

zasada zachowania

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wymowa w języku angielskim: conservation law
electroscope
electroscope

elektroskop

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wymowa w języku angielskim: electroscope

Keywords

charge conservationcharge conservationcharge conservation

total chargetotal charge total charge

isolated systemisolated system isolated system