Why does LED2 light only half time compared to LED1?

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Discussion Overview

The discussion revolves around the behavior of two LEDs (LED1 and LED2) in a circuit involving a transistor, specifically why LED2 lights for only half the time compared to LED1. The scope includes technical explanations of circuit behavior and the functioning of the transistor.

Discussion Character

  • Technical explanation, Conceptual clarification

Main Points Raised

  • One participant inquires about the reason for the difference in lighting duration between LED1 and LED2 when the input voltage is described as Us=2sinωt volts.
  • Another participant suggests considering the role of the transistor when the voltage at the base (Vs) is high.
  • A participant expresses confusion about the explanation provided, indicating that it did not clarify their question.
  • A further response elaborates on the transistor's function, describing its three nodes (Base, Emitter, Collector) and how it operates as a switch, affecting current flow through the LEDs based on the Base voltage.
  • One participant expresses understanding after the explanation, indicating that the clarification was helpful.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the initial question regarding the lighting duration of the LEDs, but there is a shared understanding of the transistor's operation as a switch affecting current flow.

Contextual Notes

The discussion does not resolve the specific conditions under which LED2 lights for only half the time compared to LED1, nor does it clarify the assumptions regarding the circuit configuration or the definitions of "high" and "low" voltage in this context.

StrongInterac
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Can anyone explain to me why LED2 light only half time compared to LED1? If Us=2sinωt volts
 

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Think about what the transistor does when Vs is "high".
 
it doesn't help me a lot...
 
That's okay, we'll review how the transistor functions in this circuit.

The transistor has 3 nodes:
The Base (left side of transistor)
The Emitter (lower-right of transistor)
The Collector (upper-right of transistor)

In this circuit, the transistor acts like a simple switch. When the Base voltage is high, you can treat it as a short between the Emitter and Collector. Which LED or LED's have any appreciable current going through them, if you short the Emitter to the Collector?

When the Base voltage is low or negative, you can treat the Emitter to Collector as an open circuit, with no appreciable current. If that's the case, which LED or LED's have an appreciable current going throw them?
 
I understand it now. Thx for the help!
 

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