Prąd elektryczny i jego natężenie

Prepare answers to the introductory questions for the lesson.

1. What is an insulator?

2. What is a conductor?

3. Indicate the basic differences in the structure of the insulator and conductor.

4. Why can electricity flow only through conductors?

1. What is electric currentelectric currentelectric current?

The bodies, which as a whole are electrically neutral, hide charges of both signs inside. We also know that there are bodies called conductors, where some of these charges (electrons or ions) are free to move. The movement of these charge carriers is chaotic. However, if an external factor arranges the movement of charges, we deal with electric currentelectric currentelectric current.

2. What is an orderly movement?

Examples of an orderly movement.

- In the lake, the water somehow moves, but in different places it does in a different direction. In the river, water moves in one direction. This is the orderly movement. It is sometimes called river current.

- Or one more comparison. Imagine you are in a Spanish city on the street. The festival is underway. People walk chaotically from place to place, jostling each other. Finally, the main attraction of the day follows: the bulls were released. The crowd begins to move one way, away from the bulls running down the street. Before the bulls were released, the street resembled a conductor where no electric currentelectric currentelectric current flows. People are free charge carriers. Bulls enforce the orderly movement of the crowd. During the current flow through a conductor we deal with such an orderly movement of charges.

- It should be emphasized that during the current flow, charges do not move quite as neatly as soldiers on a parade, but rather like a rushed running crowd. This is in addition an obstacle race, because on the way of electrons there are positive metal ions standing still.

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Rysunek przedstawia nieuporządkowany zbiór kółek ze znakiem plus, symbolizujących ładunki naładowane dodatnio oraz mniejszych kółek ze znakiem minus, symbolizujących ładunku naładowane ujemnie. Od mniejszych kółek narysowane są strzałki skierowane w prawo pod różnymi kątami, symbolizujące ruch wolnych elektronów.

3. What is the direction of electric currentelectric currentelectric current?

The direction of the current is determined conventionally as the direction of movement of positive charges. If the current carriers are negative charges, the current direction is opposite to the direction of charge movement. People agreed to determine the direction of the current flow in this way.

4. What physical quantity describes quantitatively the flow of electric currentelectric currentelectric current?

This quantity is the current intensitycurrent intensitycurrent intensity, often referred to simply as the current. Often when we are considering the strength of a phenomenon, we are talking about the intensity, e.g. about the intensity of traffic. The more cars drive on the street in a unit of time the larger the intensity of traffic. The same is with the current intensitycurrent intensitycurrent intensity. If a large charge flows through the conductor within a second, we say that there is a high current in the conductor. If during a unit of time a small charge flows, then the current is small.

So we can say that the current is an electric chargeelectric chargeelectric charge that flows through the conductor in a unit of time.

5. How to calculate the current?

If, for example, during the time t = 7 s, a charge of 14 coulombs flows, then there are 2 coulombs in one second. To find out how many coulombs flow per unit of time, the charge that flows has to be divided by the flow time.

Thus, the current is the ratio of the charge to the time it flows. The same definition expressed as a formula:

The unit of current is the ampereampereampere. The current has an intensity of one ampereampereampere, when the charge of one coulomb flows through the conductor in one second.

Current is measured using a device called an ammeter.

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Pokaz slajdów – amperomierze. 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).

Pokaz slajdów – amperomierze. 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).

Zasób interaktywny dostępny pod adresem https://zpe.gov.pl/a/DiQAbLZew

Summary

• Electric currentelectric currentElectric current is the orderly movement of free electric charges.

• Free charges - carriers of electric current - can be both negative and positive. In metals, these are electrons, in gases and liquids these are ions. According to convention, the direction of the current is consistent with the movement of positive charges, i.e. from „plus” to „minus”.

• The intensity of the current is the ratio of the charge flowing through the cross‑section of the conductor to the time when this charge has flown:

  $I=\frac{q}{t}$

  The unit of current is 1 A (ampereampereampere). The current intensitycurrent intensitycurrent intensity is equal to 1 A, when the 1 C charge flows through the cross‑section of the conductor within 1 s.

• The intensity of the electric current is measured using an ammeter.

Exercises

Glossary

Keywords

electric currentelectric currentelectric current

electric chargeelectric chargeelectric charge

electron driftelectron driftelectron drift