Question Video: Identifying the Permitted Direction of Current In a Diode | Nagwa Question Video: Identifying the Permitted Direction of Current In a Diode | Nagwa

# Question Video: Identifying the Permitted Direction of Current In a Diode Physics • Third Year of Secondary School

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Which of the following diagrams correctly shows the direction in which a diode will permit a current? [A] Diagram A [B] Diagram B

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### Video Transcript

Which of the following diagrams correctly shows the direction in which a diode will permit a current?

In both of these diagrams, we see the circuit symbol for a diode. The difference between options (A) and (B) is that in (A) current points to the right, while in (B) it points to the left. Because of how a diode is constructed, only one of these diagrams correctly shows how current travels in a diode. A diode is a circuit component that works in a simple way. It allows the flow of charge in one direction while preventing its flow in the opposite direction.

By looking at the circuit symbol, if we think of this triangle as an arrowhead, that arrowhead always points in the direction of allowed charge flow. In a similar way, we could think of this vertical line here as a barrier preventing the flow of charge coming from the opposite way. However we think of it, a diode is like a one-way switch or a valve in a circuit.

Reviewing our answer options, we see that in option (A), the current is pointed in the direction of the arrowhead, we can call it, on this diode. This, as we’ve seen, is the allowed direction of charge flow through a diode oriented this way. Diagram (B), on the other hand, shows charge flowing in the opposite direction. This is the type of charge movement that a diode is specifically designed to prevent.

So it’s answer option (A) which shows a diagram correctly depicting the direction in which a diode will permit a current.

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