Does a photo-resistor create an AC current?

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Discussion Overview

The discussion revolves around the feasibility of using a photo-resistor to create an alternating current (AC) with a frequency corresponding to light. Participants explore the characteristics of photo-resistors, the nature of light frequencies, and alternative methods to achieve high-frequency AC.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether a photo-resistor can generate an AC current with a frequency equal to the light hitting it.
  • Another participant asserts that a photo-resistor only changes resistance based on light levels and does not produce an alternating effect, noting that the current would not go negative.
  • Some participants discuss the significant difference between light frequencies and those of common electrical devices, suggesting that nothing electrical responds directly at light frequencies.
  • There are inquiries about alternative methods to achieve high-frequency AC, with suggestions including the use of radio transmitters and LEDs, but clarifications that these do not create electron flow at light frequencies.
  • Participants express uncertainty about the effectiveness of using a magnet in conjunction with high-frequency AC and question what outcomes could be expected.

Areas of Agreement / Disagreement

Participants generally agree that a photo-resistor cannot create an AC current with light frequencies, but multiple competing views remain regarding alternative methods to achieve such frequencies and the potential effects of using a magnet.

Contextual Notes

Some limitations in the discussion include the dependence on definitions of AC and the specific characteristics of devices mentioned, as well as unresolved questions about the behavior of electrons at high frequencies.

grahas
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I'm a high school physics student. I want to do an experiment to see what happens when a high frequency alternating current goes through a magnet. To create the high frequency alternating current could a photo resistor do that for me? Does the photo-resistor create an alternating current with a frequency equal to the light hitting it?
 
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No, a photoresistor can only change the value of its resistance depending on the light level, and the frequency of the light doesn't produce an alternating effect.

You could vary between lower current and higher current with a photo resistor and a battery, but that's not exactly what you're asking for (the current would never go negative). Furthermore, I don't even think photoresistors respond quickly enough to alternate the current at even moderate frequencies.
 
Is there any way to achieve an alternating current with a frequency in the range of light, via a mechanical or electrical device?
 
Not to my knowledge. The frequency of light is much, much bigger than, say, microwave frequencies.
 
Well, I'll post back the results of my experiment to close the thread, thanks for the help!
 
grahas said:
I'm a high school physics student. I want to do an experiment to see what happens when a high frequency alternating current goes through a magnet

Are you saying you want to use the magnet as a conductor? I don't think anything is going to happen. What would you like to see happen?

As for high frequency AC, your wifi network runs at 2.4GHz. Low frequency (red) light is 400,000 GHz.
http://www.laserfocusworld.com/articles/print/volume-49/issue-07/newsbreaks/world-s-fastest-photodetector-has-70-ghz-bandwidth.html
Photodetectors respond to the amplitude of the light, not the light frequency

Nothing electrical directly responds at the frequency of light.
 
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meBigGuy said:
Are you saying you want to use the magnet as a conductor? I don't think anything is going to happen. What would you like to see happen?

other than short circuiting the power supply :wink:

to the OP ... definitely not a wise thing to do
 
grahas said:
Is there any way to achieve an alternating current with a frequency in the range of light, via a mechanical or electrical device?

A radio transmitter does that. Just put your magnet next to a cell phone while talking.

What effects would you see? Probably nothing.
 
grahas said:
Is there any way to achieve an alternating current with a frequency in the range of light, via a mechanical or electrical device?

yes, the standard way is to apply the correct amount of voltage to an appropriate light globe or LED ( Light Emitting Diode)
 
  • #10
davenn said:
yes, the standard way is to apply the correct amount of voltage to an appropriate light globe or LED ( Light Emitting Diode)
Note that does not actually create a 400,000 GHz AC current (electron flow). It creates a stream of photons with a frequency of 400,000 GHz
 
  • #11
meBigGuy said:
Note that does not actually create a 400,000 GHz AC current (electron flow). It creates a stream of photons with a frequency of 400,000 GHz

yes, I realize that ... but it's about the closest he is going to get :wink::rolleyes:
 
  • #12
I got it, and was sure you knew. Just wanted him to be clear.
 
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  • #13
meBigGuy said:
I got it, and was sure you knew. Just wanted him to be clear.

:smile:

grahas said:
Is there any way to achieve an alternating current with a frequency in the range of light, via a mechanical or electrical device?

I'm not aware of any way to do what he is asking. Even in the GHz microwave bands above around 30 GHz and up to several 100 GHz,
any oscillation within a Gunn diode or similar device, doesn't as an oscillation of electrons at that freq occur outside the device ( to my knowledge)Dave
 

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