# Electric current

> Moving charges need a closed path


## Objectives

- Define electric current as a flow of electric charges.
- Explain why a current needs a source and a closed path.
- State what moves in a metal wire and in a solution of ions.

## 1. Electric current: from zero




## 2. Why does the bulb go out?

Predict: what happens to the bulb?

- It goes out ✓
- It glows more weakly
- It stays lit: the battery still has energy

Charges flow around a complete path. Cutting a wire leaves an air gap that the charges cannot cross, so the current stops and the bulb goes out.

[ar-EG] الـ charges بتسري في مسار كامل مقفول. لما السلك يتقطع بتبقى فيه فجوة هوا الـ charges مش بتقدر تعدّيها، فالـ current بيقف واللمبة بتطفي.
## 3. A flow of charges

Electric current A flow of electric charges through a conductor or a solution. Switch (0 = open, 1 = closed) The battery pushes the charges. They flow only round a closed path. In a metal wire, the moving charges are the free electrons.


## 4. In a solution, ions move

A solution can carry a current too, if it contains ions. Each ion is pulled to the plate with the opposite charge. Opposite charges attract. The ions must be free to move. In a solid salt, they are fixed in place.


## 5. Check yourself

Two plates joined to a battery touch each substance. Which one carries a current?

- Sugar dissolved in pure water
- Sodium chloride solution ✓
- Solid table salt (sodium chloride)

Sodium chloride solution carries a current because its ions are free to move to the plates. In solid salt the ions cannot move, and sugar does not form ions in water.

[ar-EG] الـ sodium chloride solution بيوصّل الـ current عشان الـ ions بتاعته حرة تتحرك ناحية الألواح. في الملح الصلب الـ ions مش بتقدر تتحرك، والسكر مش بيكوّن ions في المية.
## 6. Summary

Electric current is a flow of electric charges. It needs a source, such as a battery, and a closed path. Wire: free electrons move. Solution: ions move to the oppositely charged plate. Next: a current through a solution of metal ions can coat an object with that metal. Can you explain why cutting one wire turns the bulb off? The charges flow only round a closed path. Cutting a wire leaves an air gap that the charges cannot cross, so the current stops and the bulb goes out.



Chapter: Transition Elements (https://yaani.ai/ar/learn/chemistry/chem-s3-en.ch1)
Source: https://yaani.ai/ar/lesson/chem-s3-en.lesson-phys.electric-current