Question Video: Understanding the Direction of Conventional Current in a Circuit | Nagwa Question Video: Understanding the Direction of Conventional Current in a Circuit | Nagwa

Question Video: Understanding the Direction of Conventional Current in a Circuit Science • Third Year of Preparatory School

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Complete the following sentence: In an electric circuit, conventional current goes from the _ terminal of the cell to the _ terminal.

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Video Transcript

Complete the following sentence. In an electric circuit, conventional current goes from the blank terminal of a cell to the blank terminal. (A) Negative, positive; (B) positive, negative.

This question is asking us in which direction is the current in a circuit, the current from the negative terminal of the cell to the positive or vice versa? Why does it matter? Recall that a current is the flow of charged particles. We know that in a circuit electrons are the charged particles that move. You might also remember that when a cell is connected to a circuit, the electron current goes from the negative terminal of the cell to the positive terminal of the cell.

However, we have to be very careful here. The question isn’t asking us about electron current. The question is asking about conventional current. These are not the same thing. When scientists first discovered electric current, they did not know that current consisted of moving electrons. They knew that some kind of charged particle, called a charge carrier, was moving around the circuit, but they weren’t sure exactly what kind of particle it was or whether it was positively or negatively charged. In fact, they actually thought that the positive charges were the ones moving. This is how the term current was originally defined: the flow of positive charges around a circuit.

Today, we know that this is not true, but this convention is still often used. So, we call this hypothetical positive-charge-carrying current a conventional current. To figure out the direction of conventional current, we must remember what we know about charges attracting and repelling. Recall that unlike charges attract. This means a positive charge and a negative charge will be pulled towards each other. And like charges repel. If you had two positive charges next to each other, they would push away from each other. Therefore, positive charges would be attracted to the negative terminal of a cell and repelled by the positive terminal of the cell.

So, the conventional current must move away from the positive terminal of the cell and towards the negative terminal. The correct answer is therefore (B).

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