Question Video: Identifying the Circuit Symbol of a Diode | Nagwa Question Video: Identifying the Circuit Symbol of a Diode | Nagwa

Question Video: Identifying the Circuit Symbol of a Diode Physics • Third Year of Secondary School

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Which of the following circuit symbols represents a diode?

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Video Transcript

Which of the following circuit symbols represents a diode?

Of these five circuit symbols, we need to recognize by eye which one represents a diode. A few of these circuit symbols tend to be more common than others. For example, we can recall that the circuit symbol shown in answer option (C) represents a capacitor. In this symbol, we see the two parallel plates of the capacitor on which charge builds up. We won’t choose answer option (C) then. And in choice (A), we see something that looks like a resistor, except for this arrow drawn through it. As it turns out, this arrow indicates a variability in the resistance of the resistor represented by the symbol. In other words, it shows us a resistor whose value can be changed by some means, perhaps by turning a dial or flipping a switch. The circuit symbol shown in option (A) then is a variable resistor, and we won’t choose that.

Another type of resistor is shown to us in answer choice (D). In this symbol, the two arrows side by side represent light, incoming and landing on a resistor. This circuit symbol represents a resistor whose value depends on how much light it receives. In fact, it’s called a light-dependent resistor, or LDR for short. This also is not a diode, so we won’t choose option (D). The circuit symbol in option (B) again has parallel arrows indicating light. But this time, the light is being emitted by this circuit component. That gives us a clue as to its proper name. This is called a light-emitting diode, or LED.

From the circuit symbol, we can see that this is indeed a type of diode because of this triangle and in the line in contact with one of the corners of the triangle. These features by themselves in a circuit symbol do indicate a diode. This is what we see in answer option (E). There’s a triangle, or we could think of it as an arrowhead, indicating the allowed direction of charge flow, with the tip of that arrowhead in contact with a vertical line. The circuit symbol shown in answer option (E) represents a diode.

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