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Photoelectric Effect

Puneet Asked:

“In [wiki]photoelectric effect[/wiki] electrons emit out leaving behind positive charge then why [wiki]electron emission[/wiki] not stop after sometime.”

Ans:

The photoelectric current can continue for long only if the lost electrons are replenished by some means. Unless, the positive potential will go on increasing until a stage is reached when no more electrons can be released with the the particular frequency of incident radiation.

Photoelectric effect takes place in the case of metals which have plenty of free electrons. The electrons lodged off by light could easily be regained as there is not much energy difference from a stray electron and a free electron on the surface of a metal.

Further, in a metal, the free electrons does  not belong to a single atom, each atom is surrounded by a sea of electrons. SO it is not right to say that each electron released creates an ion each – but creates a net positive charge for each electron lost.

(Comments and further explanations from visitors solicited)

How can the electric current in a circuit be kept continuous?

Susmita asked:

  1. What is Current?
  2. How can electric current in a circuit be kept continuous?

 

Ans:

The word current means flow.

Electric Current refers to charges in motion. The most common way of producing current is by applying a potential difference across the terminals of a conductor. Then the free electrons in the conductor drifts towards the positive terminal.

The current in the circuit can be kept continuous by providing a constant potential difference between two points of the circuit. This is usually done by connecting the ends of the circuit to the terminals of an electrochemical cell (which converts chemical energy to electrical energy) or a dynamo (which converts mechanical energy to electrical energy)

Please refer the following links for more information

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