Current direction | Electrical engineering | Khan Academy

TL;DR

The positive direction of current is based on the movement of positive charges, and it is a convention that has been used for centuries.

Transcript

• [Voiceover] In the last video, we talked about the meaning of current, and current is defined to be the movement of charge, amount of charge per second. We looked at a copper wire where electrons are carrying the current, and we looked also at a salt solution where both positive and negative ions are carrying the current across this imaginary bou... Read More

Key Insights

• 😑 Current is the movement of charge per second, whether it is carried by electrons or ions.
• ⚾ The positive direction of current is based on the movement of positive charges, not electrons.
• 🥺 Ben Franklin assigned positive and negative charges without knowledge of electrons, leading to the convention of current direction.
• 🏑 Switching the direction of current would cause confusion and disruption in the field of electricity.
• 💐 The positive direction of current aligns with how electricity flows in our bodies through the movement of positive charges.
• 😒 The convention has been in use for centuries and allows for consistency in calculations and understanding.
• 😑 Current can be carried by both electrons in metals and ions in solutions.

Questions & Answers

Q: Why do we define the positive direction of current based on the movement of positive charges?

The positive direction of current is defined this way because it aligns with the convention established by Ben Franklin, who assigned positive and negative charges before the discovery of electrons. It has been the standard practice for centuries and allows for consistent understanding and calculations.

Q: Is it always electrons that carry the current?

No, current can be carried by both electrons and ions. In a copper wire, electrons carry the current, while in a salt solution, positive and negative ions can carry the current.

Q: Why haven't we switched the direction of current to align with the movement of electrons?

Switching the direction of current after centuries of convention would lead to confusion and disruption. While electrons carry the current in metals, positive charges can also move in other conductive materials, like ions in solutions. The current convention allows for consistency and ease of understanding.

Q: How is current conducted in the human body?

Current in the human body is conducted through the movement of positive charges, such as ions. This aligns with the convention of assigning the positive direction of current and is how electricity flows within our bodies.

Summary & Key Takeaways

• Current is defined as the movement of charge, and it can be carried by either electrons or ions.

• The positive sign for current represents the direction in which positive charges move.

• The convention of assigning the positive direction of current opposite to the movement of electrons goes back to Ben Franklin's assignment of positive and negative charges.