Photoelectric Cell

Physics Chemistry Biology Mathematics
Science > Physics > Electrons and Photons > You are Here

Photovoltaic Cell or Photoelectric Cell:

  • Photoelectric cell or photocell is an electronic device which works on the principle of photo-electric effect and converts light energy into electrical energy.

Construction :

photoelectric cell

  • Photocell consists of evacuated glass tube containing two electrodes emitter (C) and Collector (A)
  • The emitter is shaped in the form of a semi-hollow cylinder. It is always kept at a negative potential.
  • The collector is in the form of a metal rod and fixed at the axis of the semi-cylindrical emitter. The collector is always kept at a positive potential.
  • The glass tube is fitted on non-metallic base and pins are provided at the base for external connection.

Working:

  • The emitter is connected to negative terminal and collector is connected to positive terminal of a battery.
  • A radiation of frequency more than the threshold frequency of material of emitter is made incident on the emitter. Photo-emission takes place. The photo-electrons are attracted towards the collector which is positive w.r.t. the emitter, Thus current flows in the circuit.
  • If the intensity of incident radiation is increased the photoelectric current increases.

Applications of the Photoelectric Cell:

  • Photo-electric cell is used in the reproduction of sound which is recorded on a movie film.
  • Photo-electric cell is used in exposure meter.  The exposure meter is used along with a camera to know the correct time of exposure for having a good photograph.
  • Photo-electric cell is used in lux-meter  This device is used to determine the intensity of light.
  • Photo-electric cell is used in burglar-alarm.  This device is kept near a safe to be protected from a thief.

Use of Photoelectric Cell in Sound Reproduction from the Motion Picture:

  • Photo-electric cell is used in the reproduction of sound which is recorded on a movie film.
  • In a movie, film sound is recorded on the film of actions in the form of a thin transparent strip. This thin transparent strip is called the soundtrack.
  • The transparency of soundtrack depends on the variation of the frequency of sound recorded. Using photocell sound is reproduced from the soundtrack.
  • When the film is run in a projector the light of projector this soundtrack and falls on the photocell. Due to variation in soundtrack, the variation of intensity of sound takes place and thus the photo-electric current varies. The current is amplified and is fed to speakers.

Use of Photoelectric Cell in Burglar Alarm:

  • Photo-electric cell is used in burglar-alarm.  This device is kept near a safe to be protected from a thief. A burglar alarm is a device which is used for locating intruder, thief near precious, valuable things like safe.
  • The device consists of a photocell and infra-red source of light. The light from the infra-red source is made continuously incident on the photocell making photoelectric effect continuous. Thus the photoelectric current in the cell flows continuously.
  • When the path of infra-red light is obstructed by the thief, the light falling on photocell is cut-off and photo-electric current in the cell stops and relay circuit is activated and a siren starts hooting.



Use of Photoelectric Cell in Exposure meter:

  • Photo-electric cell is used in exposure meter.  The exposure meter is used along with a camera to know the correct time of exposure of film for having a good photograph.
  • To have a good photograph if the intensity of light is more the exposure of film should be less. If the intensity of light is less the exposure of film should be more. The exposure meter is a device attached to the camera which decides the exposure of the film.
  • Exposure meter consists of a photo-electric cell with sensitive milliammeter and battery connected in series to it. The photoelectric current produced in the cell is directly proportional to the intensity of light.
  • If deflection in the milliammeter is small the photoelectric current is small. It indicates that the intensity of light is small. Thus the exposure time should be more. If deflection in the milliammeter is large the photoelectric current is large. It indicates that the intensity of light is more. Thus the exposure time should be less.
Science > Physics > Electrons and Photons > You are Here
Physics Chemistry Biology Mathematics

3 Comments

  1. missionfor.me

    Estudio y difusión de los cuentos populares.

    • Hemant More

      It is in spanish which means "it is the act of spreading something, especially information, to common people and make it popular"

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